10.14639/0392-100X-N1981
Objectives. To determine the serum levels of interleukin-1beta (IL-1β) in patients with acquired laryngotracheal stenosis (ALTS) and healthy volunteers and compare levels between serum and tissue of the stenotic segment. Materials and methods. An exploratory cohort study included 20 participants with ALTS and 5 healthy volunteers. ALTS group was categorised into mild and severe according to grade of stenosis and presence of tracheostomy. Comparisons of serum levels of IL-1β between pre- and post-surgical intervention and between blood and tissue samples in the severe ALTS group were made. Correlation of IL-1β levels between blood and tissue was assessed using Spearman’s correlation. Results. Severe ALTS patients showed higher serum levels of IL-1β compared to mild ALTS and healthy volunteers (p = 0.045). IL-1β was higher before surgical intervention than after surgical intervention (p = 0.003). There was a strong positive correlation of IL-1β between serum and tissue (r = 0.74, p = 0.035). Conclusions. Serum levels of IL-1β are higher in ALTS patients than in healthy controls and positively correlate with tissue levels. The decreasing trend of serum IL-1β observed following successful surgical intervention reflects the absence of ongoing inflammation at the stenotic segment.
text/xml
1827-675X
1981
en
Marina  Mat Baki
http://creativecommons.org/licenses/by-nc-nd/4.0
ACTA Otorhinolaryngologica Italica
inflammatory mediators
Serum interleukin 1β in patients with acquired laryngotracheal stenosis
Text.Serial.Journal
https://www.actaitalica.it/
42
Laryngology
2022-06-30
2021-12-23
2022-07-26
2022-07-26
250-256
1
Marina  Mat Baki
2022/06/30
10.14639/0392-100X-N1981
250
Faculty of Medicine, National University of Malaysia, Kuala Lumpur, Malaysia
1827-675X
inflammatory mediators
en
256
Serum interleukin 1β in patients with acquired laryngotracheal stenosis
https://www.actaitalica.it/article/download/1981/826
42
ACTA OTORHINOLARYNGOLOGICA ITALICA 2022;42:250-256; doi: 10.14639/0392-100X-N1981




Laryngology


Serum interleukin 1b in patients with acquired
laryngotracheal stenosis
Livelli di Interleuchina 1β sierica in pazienti con stenosi laringotracheale acquisita
Norazwani Azwal1,2, Yogeswaran Lokanathan3, Mawaddah Azman1, Min Hwei Ng3, Abdullah Sani Mohamed1,
Marina Mat Baki1
1
 Faculty of Medicine, National University of Malaysia, Kuala Lumpur, Malaysia; 2 Department of Otorhinolaryngology and Head &
Neck Surgery, International Islamic University Malaysia; 3 Tissue Engineering Centre, National University of Malaysia, Kuala Lumpur,
Malaysia


SUMMARY
Objectives. To determine the serum levels of interleukin-1beta (IL-1β) in patients with ac-
quired laryngotracheal stenosis (ALTS) and healthy volunteers and compare levels between
serum and tissue of the stenotic segment.
Materials and methods. An exploratory cohort study included 20 participants with ALTS
and 5 healthy volunteers. ALTS group was categorised into mild and severe according to
grade of stenosis and presence of tracheostomy. Comparisons of serum levels of IL-1β
between pre- and post-surgical intervention and between blood and tissue samples in the
severe ALTS group were made. Correlation of IL-1β levels between blood and tissue was
assessed using Spearman’s correlation.
                                                                                                  Presentation at conference
Results. Severe ALTS patients showed higher serum levels of IL-1β compared to mild                The findings of this study were presented at the
ALTS and healthy volunteers (p = 0.045). IL-1β was higher before surgical intervention            39th General Meeting of the Malaysian Society of
than after surgical intervention (p = 0.003). There was a strong positive correlation of IL-1β    Otorhinolaryngologists - Head and Neck Surgeons.
between serum and tissue (r = 0.74, p = 0.035).
Conclusion. Serum levels of IL-1β are higher in ALTS patients than in healthy controls            Received: December 23, 2021
and positively correlate with tissue levels. The decreasing trend of serum IL-1β observed         Accepted: March 20, 2022
following successful surgical intervention reflects the absence of ongoing inflammation at
the stenotic segment.                                                                             Correspondence
                                                                                                  Marina Mat Baki
KEY WORDS: acquired laryngotracheal stenosis, interleukin-1beta, laryngeal stenosis,              Faculty of Medicine - National University of Ma-
subglottic stenosis, inflammatory mediators                                                       laysia, Department of Otorhinolaryngology
                                                                                                  9th Floor Department of Otorhinolaryngology
                                                                                                  Universiti Kebangsaan Malaysia Medical Centre
RIASSUNTO                                                                                         Kuala Lumpur, Wilayah Persekutuan, MY 56000
Obiettivi. Determinare i livelli sierici di Interleuchina-1beta (IL-1β) in pazienti con stenosi   Tel. +603-91456045. Fax +603-91456675
laringotracheale acquisita (ALTS) e volontari sani, confrontarne i livelli nel siero e nel        E-mail: marinamatbaki@ppukm.ukm.edu.my
tessuto stenotico.
Materiali e metodi. Uno studio di coorte esplorativo ha incluso 20 partecipanti con ALTS
e 5 volontari sani. Il grado di ALTS è stato classificato in lieve e grave in base alla stenosi     How to cite this article: Azwal N, Lokanathan
e alla necessità di tracheostomia. È stato effettuato il confronto dei livelli sierici di IL-1β     Y, Azman M, et al. Serum interleukin 1b in pa-
pre e post-chirurgici, e tra campioni di sangue e di tessuto nel gruppo con ALTS grave. I           tients with acquired laryngotracheal stenosis.
livelli di IIL-1β tra sangue e tessuto sono stati confrontati utilizzando la correlazione di        Acta Otorhinolaryngol Ital 2022;42:250-256.
Spearman.                                                                                           https://doi.org/10.14639/0392-100X-N1981
Risultati. I pazienti con ALTS grave hanno mostrato livelli sierici di IL-1β più elevati
rispetto a ALTS lievi e volontari sani (p = 0,045). IL-1β è risultata maggiore prima dell’in-     © Società Italiana di Otorinolaringoiatria
                                                                                                  e Chirurgia Cervico-Facciale
tervento chirurgico rispetto al post chirurgico (p = 0,003). È risultata una forte correlazio-
ne positiva di IL-1β tra siero e tessuto (r = 0,74, p = 0,035).
                                                                                                                 OPEN ACCESS
Conclusioni. Il livello sierico di IL-1β è più alto nei pazienti con ALTS rispetto al gruppo
sano ed è positivamente correlato al livello di IL-1β dei tessuti. Una tendenza alla ridu-        This is an open access article distributed in accordance with
                                                                                                  the CC-BY-NC-ND (Creative Commons Attribution-Non-
zione dell’IL-1β sierica, osservata a seguito di un intervento chirurgico con esito positivo,
                                                                                                  Commercial-NoDerivatives 4.0 International) license. The
riflette l’assenza di infiammazione in corso nel segmento stenotico.                              article can be used by giving appropriate credit and mentio-
                                                                                                  ning the license, but only for non-commercial purposes and
PAROLE CHIAVE: stenosi laringotracheale acquisita, interleuchina-1beta, stenosi                   only in the original version. For further information: https://
laringea, stenosi sottoglottica, mediatori dell’infiammazione                                     creativecommons.org/licenses/by-nc-nd/4.0/deed.en




250
                                                                                               IL-1β level in laryngotracheal stenosis




Introduction                                                     The need for multiple surgeries due to re-stenosis is com-
                                                                 mon, ranging between 28% and 70% 16.
Acquired laryngotracheal stenosis (ALTS) remains one of          The pathophysiology of ALTS is still not well understood.
the most challenging problems in otolaryngology. Studies         An inflammatory response to injury seems to play an im-
have shown that predominant causes of ALTS include trau-         portant role in the beginning of the pathogenesis of ALTS.
ma, prolonged endotracheal intubation and tracheostomy 1.        This is regulated by growth factors, cytokines, chemokines
Other less common causes include systemic diseases such          and other inflammatory mediators. Acute inflammation,
as sarcoidosis, Wegener’s granulomatosis and relapsing           which occurs in the early phase of wound healing, involves
polychondritis 2.                                                mediators of the interleukin-1 cytokine family, including
In the United States, there are an estimated 4.9 million         interleukin-1alpha (IL-1a), interleukin-1beta (IL-1b) and
cases of ALTS post-intubation and post-tracheostomy per          interleukin-1 receptor antagonist (IL-1Ra) 17. A key inflam-
year 3. Other studies have reported an incidence of laryn-       matory mediator is IL-1b, which is secreted by epithelial
gotracheal stenosis ranging from 6% to 21% 4,5. However,         cells, macrophages and neutrophils 18. IL-1b can stimulate
in Southeast Asia, the incidence rate of ALTS has not yet        the production of other inflammatory mediators such as IL-
been reported. In the authors’ centre, there were 28 cases       6, IL-8 and prostaglandin E2 (PGE2) during the inflamma-
of ALTS from August 2015 to August 2016, 10 of which             tory phase 18. Animal studies have documented that the spe-
required multiple surgical interventions.                        cific inflammatory mediators responsible for development
There is heterogeneity in the proportion of men and women        of laryngotracheal stenosis may be IL-1b and prostaglan-
reported. Some studies have reported that ALTS is more           din E2 18-22. A human study involving patients with ALTS
common in men 6, whereas others have documented a fe-            also reported markedly elevated levels of IL-1b.
male predominance 7. The age distribution may vary ac-           To the authors’ knowledge, research on adult ALTS is
cording to the aetiology of ALTS. Younger adults are the         scarce. ALTS studies have mainly focused on animal and
most common in traumatic groups (34.4 years, CI 23.5-            Caucasian participants that reported IL-1b as a possible
45.3) 8.                                                         key mediator to abnormal wound healing leading to ALTS.
Predisposing factors that may contribute to ALTS follow-         In those studies, IL-1b was measured mainly in tissue or
ing intubation include the size of the endotracheal tube, du-    secretions collected from the airway under general anaes-
ration of intubation, cuff pressure, re-intubation, history of   thesia. Therefore, the present study aimed to investigate the
tracheostomy, percutaneous tracheostomy, gastro-oesoph-          serum levels of IL-1b and its trend between ALTS (mild
ageal reflux, obesity, infection while being intubated and       and severe) and a healthy volunteer group. The levels of IL-
post-radiotherapy for neck or laryngeal tumours 5,9. ALTS        1b in blood were compared levels in tissue of the stenotic
is commonly caused by endotracheal intubation secondary          segment. To date, there have been no publications of such
to either mechanical trauma due to the placement of the en-      studies in Southeast Asia or the local population. Hence,
dotracheal tube or contact pressure. Mucosal oedema and          the present study may highlight the need for better screen-
hyperaemia may progress to mucosal necrosis and ulcera-          ing, prevention and treatment for ALTS.
tion that may occur within hours of intubation. Subsequent-
ly, this may result in exposure of the perichondrium of the
cartilage, leading to perichondritis, which can then progress    Materials and methods
to formation of scar tissue and stenosis. The formation of a     Study design and patient recruitment
stenosis may also contribute to abnormal wound healing by        An exploratory study (cohort study) was conducted over 18
dense fibrous tissue, which is further attributed to altered     months from 1st January 2017 to 30th June 2018. Twenty pa-
fibroblast responsiveness to anti-fibroblastic signals during    tients ≥ 18 years old who were diagnosed with ALTS and at-
mucosal repair 10,11.                                            tended the otorhinolaryngology (ORL) clinic were recruited.
Motor vehicle accidents (MVA) causing neck trauma and            The causes of stenosis were mainly faulty intubation, and
other injuries needing emergency intubation are other com-       one patient had stenosis following blunt laryngeal trauma.
mon aetiologies of ALTS. The number of MVA cases in              Five healthy volunteers ≥ 18 years old were also recruited
Malaysia is increasing 12. This may hypothetically increase      among the patients’ family members and clinical staff.
the incidence of ALTS. Surgical interventions with either        ALTS patients with the following criteria were excluded:
an endolaryngeal or external approach have remained the          1) non-Malaysian; 2) laryngotracheal stenosis of other
standard treatment for ALTS 13. However, these surgical          causes such as a tumour, tuberculosis, idiopathic, or con-
procedures may cause further scarring, re-stenosis and           genital; and 3) presence of co-morbidities such as autoim-
even mortality, with rates ranging from 1.8% 14 to 5% 15.        mune or chronic inflammatory diseases including eczema



                                                                                                                                251
N. Azwal et al.




and allergy rhinitis. Healthy volunteers with co-morbidities     tion, as well as serum and tissue levels of IL-1β. The corre-
or upper respiratory infection or any infection at other parts   lation between serum and tissue levels was assessed using
of the body or surgeries within one month were excluded.         Pearson’s correlation. The trends in serum IL-1β at differ-
For the ALTS group, the severity of stenosis was diagnosed       ent time points are reported descriptively.
by performing direct laryngoscopy under general anaesthe-
sia. The degree of stenosis was documented by using Cotton       Results
Myer (CM) grading 18. During clinic visits following diagno-
sis or surgical interventions, a flexible nasopharyngolaryn-     Demography
goscopy under topical anaesthesia with 2% lidocaine was          The ALTS group included 14 males and 11 females with a
performed to examine the glottis and subglottic areas. The       mean age of 48.5 years. The majority of the patients were
severity of the stenosis was then documented. Among those        Malay, followed by Chinese and Indian. Five patients had
not using a tracheostomy tube, the severity of symptoms          mild ALTS, and 15 patients were classified as having severe
was graded using the Modified Medical Research Council           ALTS. With regards to CM grading of stenosis, grades I,
(MMRC) dyspnoea scale 20. Based on severity of symptoms          II, III, and IV were 30%, 25%, 30%, and 15% of the study
and stenosis and the presence of tracheostomy, ALTS pa-          sample, respectively. Subglottic (60%) was the most com-
tients were categorised as mild or severe stenosis. Criteria     mon site of stenosis, followed by tracheal (30%), supraglot-
for the severe group included CM grading high grade 2, 3, or     tic (5%) and mixed (5%). Fifteen patients (75%) had mature
4 requiring tracheostomy and undergoing surgical interven-       scars, while five patients (25%) had granulation tissue at the
tions such as T-tube insertion, endolaryngeal laser surgery,     stenotic segment. Most patients presented with a circumfer-
dilation and open surgery, i.e. tracheal resection anastomosis   ential stenosis and all had mobile bilateral vocal folds.
(TRA). Successful surgical intervention was defined as ei-
ther successful decannulation of tracheostomy tube or relief     Surgical interventions performed for severe ALTS
of upper airway obstruction symptoms for patients who were       Of 15 patients with severe stenosis, two had a T-Tube in-
not on tracheostomy tube. Patients with CM grade I who did       serted, nine underwent transoral laser microsurgery (TLM)
not require tracheostomy and did not undergo surgical in-        and balloon dilation, two underwent TRA and two did not
tervention were categorised as mild ALTS. Blood samples          receive any surgical interventions other than tracheostomy
were taken four times from each ALTS patient every 6 to          during the study period. One had failed TRA and the other
12 weeks. For ALTS patients who required surgical inter-         was at high risk for cardiac complications for TRA; there-
ventions, apart from blood samples, tissue biopsies from the     fore, a T-tube was inserted for these two patients.
stenotic area were taken under general anaesthesia in the op-
erating theatre. Repeat blood samples were taken within 6 to     Comparison of mean of IL-1b in mild, severe ALTS and
12 weeks of post-surgical intervention. For healthy volun-       healthy volunteer groups in blood
teers, one blood sample was taken.                               The mean and SD values of IL-1β for the healthy volun-
                                                                 teer, mild and severe ALTS group were 2.310 ± 1.606,
ELISA                                                            4.127 ± 1.421 and 8.269 ± 5.848 pg/ml, respectively. The
IL-1β levels were measured in blood and tissue samples by        level of IL-1β was significantly higher in the severe ALTS
enzyme-linked immunosorbent assay (ELISA) (RayBio®               group than in the mild ALTS group. It was also signifi-
Human IL-1 beta ELISA kit), according to the manufactur-         cantly higher in the mild ALTS group compared to healthy
er’s instructions. The minimum detectable dose of IL-1β is       volunteers (p = 0.045) (Fig. 1).
reported as 0.3 pg/ml, with intra-assay and inter-assay co-
efficients of variation of < 10% and < 12%, respectively 21.     Comparison of mean IL-1b between blood and tissue sam-
                                                                 ples in severe ALTS
Statistical analysis                                             The level of IL-1b in tissue samples was found to be sig-
All data were computerised and analysed using SPSS ver-          nificantly higher than in blood samples. (p ≤ 0.05) (Fig. 2).
sion 23.0 and Graph Pad Prism version 7.0. The mean              The level of IL-1b in serum was strongly correlated with
serum levels of IL-1β for mild and severe stenosis in the        the level of IL-1b in tissue (r = 0.74, p = 0.035).
ALTS group and the healthy volunteer group were recorded
in terms of mean and standard deviation (SD). One-way            Comparison of mean serum level of IL-1b pre- and post-
ANOVA was used to analyse the mean differences in IL-1β          intervention in severe ALTS
levels between groups. A paired t-test was used to compare       Mean and SD of IL-1β for the pre- and post-intervention
the serum levels of IL-1β pre- and post-surgical interven-       group were 10.62 ± 6.814 and 4.756 ± 3.061 pg/ml, respec-



252
                                                                                                                IL-1β level in laryngotracheal stenosis




Figure 1. Differences in mean IL-1b between mild, severe ALTS and healthy   Figure 3. Comparison of the mean values of IL-1β in the severe ALTS group
volunteer groups in blood samples (p = 0.045).                              pre-and post-intervention.


                                                                            blood sample was slightly higher than that in healthy vol-
                                                                            unteers.
                                                                            Tracheal resection and anastomosis
                                                                            There was a marked reduction in IL-1β levels following
                                                                            successful surgical intervention with TRA. A reduction
                                                                            was observed together with improvement in CM grading of
                                                                            the stenosis (Figs. 4, 5). However, the IL-1β level was still
                                                                            higher than in healthy volunteers.
                                                                            Tracheostomy
                                                                            In a severe ALTS patient who had not undergone surgical
                                                                            intervention during the study period and was on tracheosto-
                                                                            my, there was a fluctuation of the IL-1β level, and the mean
                                                                            value was higher than in healthy individuals. CM grading
Figure 2. Comparison of mean IL-1b between blood and tissue samples in      was maintained as Grade 2.
the severe ALTS group.
                                                                            The trend of IL-1β level in mild ALTS and its correlation
                                                                            with CM Grading compared with mean of IL-1β in healthy
tively. Using Paired t-test, a significant reduction of IL-1b               individuals
after surgical intervention was observed (p ≤ 0.05) (Fig. 3).               The level of IL-1β was found to be low and was not above
                                                                            4 pg/ml, which correlated with the severity of the stenosis,
Examples of cases in the severe ALTS group showing trends                   but still higher than in healthy individuals.
of IL-1b over time
T-tube procedure                                                            Discussion
The level of IL-1β in patients who underwent T-tube in-                     ALTS is a condition commonly caused by emergency intu-
sertion was noted to be stagnant at around 4 to 5 pg/ml.                    bation injury 1. Moderate to severe cases of ALTS are tra-
Although stagnant, the level was higher than mean IL-1β                     cheostomy tube dependent, and those who suffer complete
in healthy volunteers.                                                      stenosis will be aphonic. This reduces the quality of life
TLM and balloon dilation                                                    and is highly likely to cause job loss. Treatment for moder-
There was a decrease in the level of IL-1β following TLM                    ate to severe ALTS, especially with poor prognostic factors,
and balloon dilation procedure. The improvement of CM                       remains one of the most challenging conditions to treat in
grading was observed together with a reduction of IL-1β.                    otolaryngology. To date, there is still a lack of studies to
However, the IL-1β level documented after taking the 4th                    identify preventive or curative medical treatment for ALTS.



                                                                                                                                                 253
N. Azwal et al.




                                                               mally can only be done when performing direct laryngosco-
                                                               py under general anaesthesia. This would not be ideal if this
                                                               inflammatory marker were to be used as a screening tool for
                                                               patients who will potentially develop ALTS. Identification
                                                               of inflammatory markers using blood samples would be an
                                                               easier and less invasive method as a screening tool. Hence,
                                                               the present study measured the levels of IL-1β in blood sam-
                                                               ples from healthy volunteers and those with mild to severe
                                                               ALTS to compare the differences. Furthermore, the trend of
                                                               IL-1β level was studied at four different time points with 6-
                                                               to 12-week intervals between each point, and the mean level
                                                               was compared between pre- and post-surgical interventions
                                                               to illustrate the impact of the inflammatory mediator. As far
                                                               as we know, no previous literature has investigated the serum
                                                               levels of IL-1β in these patients. This study is also the first
                                                               published data from Southeast Asia and may become the ba-
                                                               sis for future studies.
Figure 4. Findings before open surgery with TRA.               In the present study, the mean serum level of IL-1β in
                                                               healthy volunteers was 2.310 ± 1.606 pg/ml. When this
                                                               was compared with ALTS patients, the mean IL-1β level
                                                               was significantly higher in the latter (p < 0.05). The mean
                                                               of IL-1β was also higher in the severe ALTS group than in
                                                               the mild ALTS group (p < 0.05). In the mild ALTS group,
                                                               the levels of IL-1β remained low (≤ 4 pg/ml) throughout the
                                                               study period, which correlated with severity of the stenosis.
                                                               The level of IL-1β was found to be in a downward trend in
                                                               severe ALTS following successful TLM and open surgery.
                                                               However, the level was unchanged in patients with T-tubes
                                                               and fluctuant in patients on tracheostomy. The serum level
                                                               of IL-1β in patients who were still on T-tubes was noted to
                                                               be stagnant at around 4 to 5 pg/ml, which, however, was
                                                               still higher compared to healthy individuals.
                                                               The level of IL-1β in tissue samples was shown to be sig-
                                                               nificantly higher than in blood samples. However, a signifi-
                                                               cant positive strong correlation between blood and tissue
Figure 5. Findings after open surgery with TRA.
                                                               samples was seen in this study (r = 0.74), and this result
                                                               shows that blood samples may be used instead of tissue
                                                               samples in ALTS.
The majority of studies have been performed in animals
                                                               In a study by Puyo et al., significant tracheal inflammation
and are very scarce in humans. Preventive or curative medi-
                                                               was detected in short-term intubations. This further justi-
cal treatment may be possible by identifying the key me-
                                                               fies the abhorrent risks of persistent inflammation faced by
diators of the inflammatory response in a high risk group
                                                               patients who were intubated longer and hence high levels
of patients who have the propensity of developing ALTS.        of IL-1β 23. To our knowledge, numerous studies have been
The present study was a human study in which the serum         performed to determine IL-1β levels in ALTS, but the levels
levels of IL-1β were measured in patients diagnosed with       were mainly measured from specimens taken from tissue
mild or severe ALTS as well as in healthy volunteers. This     or secretions of the upper airway. Results of these studies
study was intended to obtain information concerning ALTS       showed that subglottic injury was associated with increased
that has not been previously reported in human studies. Pre-   levels of IL-1β 18,19,22. Another study also compared the lev-
vious studies documented IL-1β as the key inflammatory         els of IL-1β in ALTS in humans and animals 19. Granulation
mediator in ALTS 18,19. Those studies mainly measured IL-      tissue was taken from 10 patients with early symptomatic
1β in tissue samples taken from the upper airway, which nor-   subglottic stenosis and compared to mucosal tissue from



254
                                                                                                         IL-1β level in laryngotracheal stenosis




the control bronchus of the same patients. The expression        mental Grant (FF-2017-036) and the Malaysian Society of
levels of 24 different cytokines were measured by polymer-       Otorhinolaryngology and Head and Neck Surgeons (MSO-
ase chain reaction (PCR). The results showed that IL-1β          HNS) grant.
was markedly elevated in the granulation tissue compared
to the mucosa of the normal bronchus. In the same publi-         Authors’ contributions
cation, the authors also demonstrated increased IL-1β in         NA: research proposal, data collection, data analysis,
animal models of induced subglottic injury compared to the       manuscript writing. YL: data collection, data analysis,
control group.                                                   manuscript writing. ANMH: manuscript writing. MA: data
While previous studies have documented increased levels          collection, data analysis, manuscript writing. ASM: manu-
of IL-1β in tissue, the present study measures IL-1β levels      script writing. MMB: research idea and design, data collec-
in blood, which is a less invasive approach and thus a more      tion, data analysis, manuscript writing.
feasible screening tool. Additionally, we compared healthy
and ALTS groups, and mild and severe groups of ALTS,             Ethical consideration
pre- and post-surgical intervention, and correlated the level    This study was registered with the Secretariat for Research
of IL-1β with clinical findings, which were not mentioned        and Innovation and received full ethics approval with pro-
in the previous studies. This makes this research a novel        ject code FF-2017-036.
and innovative study, allowing it to be used as a baseline       The research was conducted ethically, with all study pro-
for in-depth research including clinical trials in the future.   cedures being performed in accordance with the require-
Some recent studies have demonstrated that IL-4 is elevat-       ments of the World Medical Association’s Declaration of
ed in ALTS. This is based on the role of cytokines in other      Helsinki.
fibroproliferative diseases such as idiopathic pulmonary fi-     Written informed consent was obtained from each partici-
brosis and cardiac fibrosis 24. However, there have been no      pant/patient for study participation and data publication.
comparisons between IL-1β and IL-4. Further investigation
is recommended to compare these two groups of interleu-          References
kins in the future for a better understanding of the patho-
                                                                 1
                                                                      Koshkareva Y, Gaughan JP, Soliman AMS. Risk factors for adult lar-
physiology of ALTS.                                                   yngotracheal stenosis: a review of 74 cases. Ann Otol Rhinol Laryngol
Some limitations were identified in this study. The small             2007;116:206-210. https://doi.org/10.1056/nejm199701233360422
number of patients included and the variation in the dura-       2
                                                                      Bacon JL, Patterson CM, Madden BP. Indications and interventional
tion of onset of ALTS before recruitment may limit the                options for non-resectable tracheal stenosis. J Thoracic Dis 2014;6:258-
strength of the results. For future studies, including pa-            270. https://dx.doi.org/10.3978%2Fj.issn.2072-1439.2013.11.08
tients undergoing emergency intubation in a larger cohort
                                                                 3
                                                                      Poetker DM, Ettema SL, Merati AL, et al. Association of airway ab-
                                                                      normalities and risk factors in 37 subglottic stenosis patients. Otolar-
study is recommended to confirm our findings. It would                yngol Head Neck Surg 2006;135:434-437. https://doi.org/10.1016/j.
also be interesting to investigate the association of genetic         otohns.2006.04.013
predisposition and high IL-1β in the development of ste-         4
                                                                      Moe KS, Schmid S, Weymuller JR, et al. Percutaneous trache-
nosis.                                                                ostomy: a comprehensive evaluation. Ann Otol Rhinol Laryngol
                                                                      1999;108:384-391. https://doi.org/10.1177/000348949910800412
                                                                 5
                                                                      Whited RE. A Prospective study of laryngotracheal sequelae in
Conclusions                                                           long-term intubation. Laryngoscope 1984;94:367-377. https://doi.
                                                                      org/10.1288/00005537-198403000-00014
This study documented that the normal mean serum levels          6
                                                                      Jović RM, Dragičević D, Gašić J, et al. Laryngotracheal stenosis and
of IL-1b was 2.310 ± 1.606. Levels of IL-1b were generally            restenosis. What has the influence on the final outcome? Eur Arch
higher in the adult ALTS group than in healthy volunteers.            Otorhinolaryngol 2012;269:1805-1811. https://doi.org/10.1007/
                                                                      s00405-012-1940-8
Serum IL-1β was also positively correlated with tissue lev-      7
                                                                      McCaffrey TV.          Classification     of     laryngotracheal      ste-
els, and thus blood may be used for future studies on key             nosis.      Laryngoscope        1992;102:1335-1340.           https://doi.
inflammatory mediators in ALTS.                                       org/10.1288/00005537-199212000-00004
                                                                 8
                                                                      Gelbard A, Francis DO, Ongkasuwan J, et al. Causes and consequenc-
Conflict of interest statement                                        es of adult laryngotracheal stenosis. Laryngoscope 2014;125:1137-
The authors declare no conflict of interest.                          1143. https://doi.org/10.1002/ lary.24956
                                                                 9
                                                                      Halum SL, Ting JY, Merati AL, et al. A multi-institutional analysis of
                                                                      tracheotomy complications. Laryngoscope 2011;122:38-45. https://
Funding                                                               doi.org/10.1002/lary.22364
This is not an industry-supported study. The study was           10
                                                                      Singh T, Sandulache VC, Hebda PA, et al. Subglottic stenosis ex-
funded by the Universiti Kebangsaan Malaysia Funda-                   amined as a fibrotic response to airway injury characterized by al-




                                                                                                                                          255
N. Azwal et al.




     tered mucosal fibroblast activity. Arch Otolaryngol Head Neck Surg         18
                                                                                     Sandulache VC, Chafin JB, Hebda PA, et al. Elucidating the role of
     2010;136:163. https://doi.org/10.1001/archoto.2009.175                          interleukin 1β and prostaglandin E2 in upper airway mucosal wound
11
     Papla B, Dyduch G, Olechnowicz H, et al. Post-intubation tra-                   healing. Arch Otolaryngol Head Neck Surg 2007;133:365. https://doi.
                                                                                     org/10.1001/archotol.133.4.365
     cheal stenosis - morphological-clinical investigations. Pol J Pathol
     2003;54:261-266.
                                                                                19
                                                                                     Haft S, Lee JY, Mirza N, et al. Inflammatory protein expres-
                                                                                     sion in human subglottic stenosis tissue mirrors that in a murine
12
     Hussin WMTW, Masron T. Trend analysis and spatial patterns of                   model. Ann Otol Rhinol Laryngol 2014;123:65-70. http://doi.
     fatal traffic accidents in Malaysia: a case study of the Timur Laut Dis-        org/10.1177/0003489414521146
     trict, Penang. Geografia-Malaysian J Soc Space 2017;11(13).                20
                                                                                     Nouraei SAR, Nouraei SM, Sandhu GS, et al. Sensitivity and respon-
13
     Ciccone A, Degiacomo T, Rendina E, et al. Operative and non-op-                 siveness of the medical research council dyspnoea scale to the pres-
     erative treatment of benign subglottic laryngotracheal stenosis. Eur            ence and treatment of adult laryngotracheal stenosis. Clin Otolaryngol
     J Cardiothoracic Surg 2004;26:818-822. https://doi.org/10.1016/j.               2008;33:575-580. https://doi.org/10.1111/j.1749-4486.2008.01832.x
     ejcts.2004.06.020                                                          21
                                                                                     Leng SX, McElhaney JE, Kuchel GA, et al. ELISA and multiplex
14
     Grillo HC, Mathisen DJ. Surgical management of tracheal stric-                  technologies for cytokine measurement in inflammation and aging
     tures. Surg Clin North Am 1988;68:511-524. https://doi.org/10.1016/             research. J Gerontol A Biol Sci Med Sci 2008;63:879-884. https://
     s0039-6109(16)44531-7                                                           dx.doi.org/10.1093%2Fgerona%2F63.8.879
15
     Brichet A, Verkindre C, Marquette CH, et al. Multidisciplinary ap-
                                                                                22
                                                                                     Puyo CA, Dahms TE. Innate immunity mediating inflammation sec-
                                                                                     ondary to endotracheal intubation. Arch Otolaryngol Head Neck Surg
     proach to management of postintubation tracheal stenoses. Eur Respir
                                                                                     2012;138:854. https://doi.org/10.1001/archoto.2012.1746
     J 1999;13:888. https://doi.org/10.1034/j.1399-3003.1999.13d32.x
                                                                                23
                                                                                     Branski RC, Verdolini K, Hebda PA, et al. Markers of wound
16
     Hirshoren N, Eliashar R. Wound-healing modulation in upper airway               healing in vocal fold secretions from patients with laryngeal pa-
     stenosis-Myths and facts. Head Neck 2009;31:111-126. https://doi.               thology. Ann Otol Rhinol Laryngol 2004;113:23-29. https://doi.
     org/10.1002/hed.20925                                                           org/10.1177/000348940411300105
17
     Rijkers K, Majoie HJ, Vles JS, et al. The role of interleukin-1 in sei-    24
                                                                                     Motz KM, Yin LX, Hillel AT, et al. Quantification of inflammatory
     zures and epilepsy: A critical review. Exp Neurol 2009;216:258-271.             markers in laryngotracheal stenosis. Otolaryngol Head Neck Surg
     https://doi.org/10.1016/j.expneurol.2008.12.014                                 2017;157:466-472. https://doi.org/10.1177/0194599817706930




256
