10.5826/dpc.1401a46
Introduction: Recurrent aphthous stomatitis (RAS) is a prevalent ulcerative condition affecting oral mucosa.
Objectives: A systematic review and meta-analysis was performed to compare the level of neutrophil to lymphocyte ratio (NLR) between individuals with RAS and those who are healthy.
Methods: A systematic search for relevant publications before June 21, 2022, was conducted using Web of Science, PubMed, and Scopus. The results were presented as the standardized mean difference (SMD) with a 95% confidence interval (CI), and a random-effects model was used to calculate pooled effects due to the presence of significant heterogeneity. Quality assessment was performed using the Newcastle-Ottawa scale.
Results: Overall, 13 article with were included in the analysis. NLR was higher among patients with RAS compared to healthy controls (SMD = 0.50, 95% CI = -0.20 to 0.79, P = 0.001, I2 = 91.5%). In the subgroup analysis based on the study design, it was found that retrospective studies showed higher levels of NLR in patients with RAS compared to healthy controls (SMD = 0.62, 95% CI= 0.16 to 1.08, P &lt; 0.01), but these results were not applied to prospective studies (SMD = 0.35, 95% CI = -0.03 to 0.74, P &lt; 0.07).
Conclusion: Elevated neutrophil to lymphocyte ratio revealed crosstalk between systematic inflammation and RAS.
text/xml
2160-9381
3434
en
Shokoufeh Khanzadeh
https://creativecommons.org/licenses/by-nc/4.0
Dermatology Practical & Conceptual
inflammation
Diagnostic Significance of Neutrophil to Lymphocyte Ratio in Recurrent Aphthous Stomatitis: A Systematic Review and Meta-Analysis 
Text.Serial.Journal
https://dpcj.org/index.php/dpc
Review
2024-01-31
2023-04-14
2024-01-31
2024-02-21
e2024046
Dermatol Pract Concept
Introduction: Recurrent aphthous stomatitis (RAS) is a prevalent ulcerative condition affecting oral mucosa.
Objectives: A systematic review and meta-analysis was performed to compare the level of neutrophil to lymphocyte ratio (NLR) between individuals with RAS and those who are healthy.
Methods: A systematic search for relevant publications before June 21, 2022, was conducted using Web of Science, PubMed, and Scopus. The results were presented as the standardized mean difference (SMD) with a 95% confidence interval (CI), and a random-effects model was used to calculate pooled effects due to the presence of significant heterogeneity. Quality assessment was performed using the Newcastle-Ottawa scale.
Results: Overall, 13 article with were included in the analysis. NLR was higher among patients with RAS compared to healthy controls (SMD = 0.50, 95% CI = -0.20 to 0.79, P = 0.001, I2 = 91.5%). In the subgroup analysis based on the study design, it was found that retrospective studies showed higher levels of NLR in patients with RAS compared to healthy controls (SMD = 0.62, 95% CI= 0.16 to 1.08, P &lt; 0.01), but these results were not applied to prospective studies (SMD = 0.35, 95% CI = -0.03 to 0.74, P &lt; 0.07).
Conclusion: Elevated neutrophil to lymphocyte ratio revealed crosstalk between systematic inflammation and RAS.
Shokoufeh Khanzadeh
2024/01/31
10.5826/dpc.1401a46
e2024046
Student Research Committee, Tabriz University of Medical Sciences, Tabriz, Iran
2160-9381
inflammation
en
e2024046
Azab, B., M. Camacho-Rivera, and E. Taioli, Average values and racial differences of neutrophil lymphocyte ratio among a nationally representative sample of United States subjects. PloS one, 2014. 9(11): p. e112361-e112361.
Diagnostic Significance of Neutrophil to Lymphocyte Ratio in Recurrent Aphthous Stomatitis: A Systematic Review and Meta-Analysis 
https://dpcj.org/index.php/dpc/article/download/3434/2564
      Diagnostic Significance of Neutrophil
   to Lymphocyte Ratio in Recurrent Aphthous
Stomatitis: A Systematic Review and Meta-Analysis
 Mohammad Javad Rahimi1, Fariba Mirakhori2, Rebecca Zelmanovich3, Christina Sedaros4,
   Brandon Lucke-Wold5, Gersham Rainone6, Arshin Ghaedi7, Shokoufeh Khanzadeh8


1 Department of Pediatric Dentistry, Shiraz University of Medical Sciences, Shiraz, Iran
2 Zanjan University of Medical Science, Zanjan, Iran
3 University of Central Florida, Orlando, USA
4 University of Florida, Gainesville, USA
5 Department of Neurosurgery, University of Florida, Gainesville, USA
6 Drexel University College of Medicine, USA
7 Student Research Committee, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran
8 Student Research Committee, Tabriz University of Medical Sciences, Tabriz, Iran



Key words: Neutrophil to lymphocyte ratio, inflammation, recurrent aphthous stomatitis, meta-analysis
Citation: Rahimi MJ, Mirakhori F, Zelmanovich R, et al. Diagnostic Significance of Neutrophil to Lymphocyte Ratio in Recurrent
Aphthous Stomatitis: A Systematic Review and Meta-Analysis. Dermatol Pract Concept. 2024;14(1):e2024046. DOI: https://doi
.org/10.5826/dpc.1401a46
Accepted: August 14, 2023; Published: January 2024
Copyright: ©2024 Rahimi et al. This is an open-access article distributed under the terms of the Creative Commons Attribution-
NonCommercial License (BY-NC-4.0), https://creativecommons.org/licenses/by-nc/4.0/, which permits unrestricted noncommercial use,
distribution, and reproduction in any medium, provided the original authors and source are credited.
Funding: None.
Competing Interests: None.
Authorship: All authors have contributed significantly to this publication.
Corresponding Author: Shokoufeh Khanzadeh, Student Research Committee, Tabriz University of Medical Sciences, Tabriz, Iran.
E-mail: Khshokufeh7@gmail.com




  ABSTRACT             Introduction: Recurrent aphthous stomatitis (RAS) is a prevalent ulcerative condition affecting oral
                       mucosa.
                       Objectives: A systematic review and meta-analysis was performed to compare the level of neutrophil
                       to lymphocyte ratio (NLR) between individuals with RAS and those who are healthy.
                       Methods: A systematic search for relevant publications before June 21, 2022, was conducted using
                       Web of Science, PubMed, and Scopus. The results were presented as the standardized mean difference
                       (SMD) with a 95% confidence interval (CI), and a random-effects model was used to calculate pooled
                       effects due to the presence of significant heterogeneity. Quality assessment was performed using the
                       Newcastle-Ottawa scale.




Review | Dermatol Pract Concept. 2024;14(1):e2024046                                                                                1
                      Results: Overall, 13 article with were included in the analysis. NLR was higher among patients with
                      RAS compared to healthy controls (SMD = 0.50, 95% CI = -0.20 to 0.79, P = 0.001, I2 = 91.5%). In
                      the subgroup analysis based on the study design, it was found that retrospective studies showed higher
                      levels of NLR in patients with RAS compared to healthy controls (SMD = 0.62, 95% CI= 0.16 to 1.08,
                      P < 0.01), but these results were not applied to prospective studies (SMD = 0.35, 95% CI = -0.03 to
                      0.74, P < 0.07).
                      Conclusion: Elevated neutrophil to lymphocyte ratio revealed crosstalk between systematic
                      ­inflammation and RAS.




Introduction                                                       inflammatory markers and cells have been the subject of
                                                                   investigations thus far. Such studies reveal elevations of
Recurrent aphthous stomatitis (RAS) is a prevalent ulcer-          proinflammatory cytokines, Th1 responses and neutrophil
ative condition affecting oral mucosa. It is characterized by      hyperactivity [9-12]. More recently, researchers have also
painful, recurrent ulcerative lesions most commonly found          looked to evaluate neutrophil-to-lymphocyte (NLR) values
on non-keratinized surfaces of the buccal mucosa, lips,            in this patient population. NLR is an emerging marker of
tongue and floor of mouth [1]. They may be single or multi-        chronic inflammation which has demonstrated strong prog-
ple in number and are described as well-demarcated, round          nostic utility in a variety of inflammatory and chronic dis-
or ovoid, and superficial [1]. RAS is estimated to affect ap-      ease states. NLR values have been shown to reflect severity
proximately 20% population, most often arising in the sec-         of systemic inflammation and predict disease outcomes in
ond decade of life [2,3]. It has important impacts on quality      a variety of malignancies, acute infections and chronic dis-
of life, causing significant pain and difficulties with speech     eases [13]. It can be readily obtained from a standard hemo-
and mastication [4,5].                                             gram and is of minimal cost to patient and provider.
    There are three primary categories of RAS, including mi-
nor RAS, major RAS and herpetiform RAS [1]. Minor RAS
                                                                   Objectives
is the most common form, accounting for greater than 70%
of cases and is considered the least severe presentation [1]. It   To date, studies evaluating NLR in RAS patients have sug-
is limited to the lips, tongue, and buccal mucosa; they are su-    gested that such a measure is elevated in this patient co-
perficial, <10mm in diameter and resolve within two weeks.         hort; however, results are mixed and overall association
Major RAS is more severe, extending into the soft palate and       remains inconclusive. As a result, a systematic review and
pharynx, averaging >10mm and lasting up to six weeks [1].          meta-analysis of the current literature is warranted. In this
Finally, herpetiform RAS consists of deeper ulcers, that are       study, we aim to evaluate the current literature to clarify this
numerous in number, which will coalesce and resolve within         important association. The results of this study can help to
30 days [1].                                                       validate NLR as a marker of RAS, further elucidating disease
    Despite its wide prevalence, the pathophysiology               pathogenesis and shaping clinical management.
of RAS remains elusive [3]. Histopathologically, the ul-
cers of RAS patients are characterized by substantial              Methods
cell-mediated ­inflammation, including infiltration of neutro-
phils, ­monocytes, and T-cells [6,7]. Such evidence suggests       The study adhered to the Preferred Reporting Items
an immunologic role in disease pathogenesis, specifically          for Systematic Reviews and Meta-Analyses (PRISMA)
cell-mediated ­
              immunity. It is currently hypothesized that          guidelines [14]. Two independent investigators conducted
                                                                   ­
underlying genetic and immunologic factors may predispose          the study selection, data extraction, and quality evaluation.
an individual to RAS [3,8]. In the setting of triggers, such       Any disagreements were resolved through discussion.
individual may develop a dysregulated immune response di-
rected toward localized areas of the oral mucosa. Suggested        Literature Search
triggers include mechanical injury, systemic disease, viral or     The search was systematically conducted on PubMed,
bacterial ­infections, and food allergies - among others [3].      ­Scopus, and Web of Science databases until June 21, 2022,
    In this context, much research has attempted to char-          using specific terms adjusted accordingly for each database:
acterize the immune response in these patients to better           ((“neutrophil”[All Fields] AND “lymphocyte”[All Fields]
understand, treat and predict prognosis of disease. Several        AND “ratio”[All Fields]) OR “Neutrophil-to-lymphocyte



2                                                                             Review | Dermatol Pract Concept. 2024;14(1):e2024046
ratio”[All Fields] OR “NLR”[All Fields]) AND (“recur-               Given the significant heterogeneity among studies, a
rent”[All Fields] ) AND ((“aphthous”[All Fields] AND             sensitivity analysis was conducted. Additionally, subgroup
“stomatitis”[All Fields]) OR “stomatitis, aphthous”[MeSH         analysis was conducted based on the study design, and pub-
Terms]). To exclude irrelevant research to the greatest ex-      lication bias was assessed using a funnel plot and an asym-
tent possible, we required the specified keywords mentioned      metry test. The Egger test was used to identify the presence
earlier to appear in the title or abstract. Additionally, we     of publication bias by analyzing the value of p. STATA 12.0
searched the references of the included studies to incorpo-      was used for all analyses, and statistical significance was
rate as many relevant studies as possible. Any references that   considered at P < 0.05, unless provided otherwise.
did not provide appropriate information were excluded. Our
search was not limited by date or language.                      Certainty of Evidence
                                                                 We utilized the Grading of Recommendations Assessment,
Inclusion and Exclusion Criteria                                 Development, and Evaluation (GRADE) technique to eval-
This meta-analysis included studies that met the following       uate the certainty of the evidence for the outcome that was
criteria: (1) a comparative design with a case group and a       studied in our review [15].
control group. The control group consisted of healthy indi-
viduals matched to the case group, which included patients
                                                                 Results
with RAS; (2) data on NLR levels in the study must be avail-
able, including mean and standard deviation; (3) the test        Search Results and Included Studies
samples must be taken from blood. Studies were excluded          After conducting a database search and a manual search of
if they met the following criteria: (1) duplicated a previous    the article citation list, we identified a total of 210 results.
publication; (2) included other conditions that may affect       Eventually, we included 13 papers [16-28] in our systematic
NLR levels; (3) were animal experiments.                         review and meta-analysis, after eliminating duplicates and
                                                                 irrelevant records. The detailed process of inclusion and ex-
Data Extraction and Conversion                                   clusion is presented in Figure 1, which shows the PRISMA
Two reviewers extracted data independently from all the          flow diagram.
studies that met the inclusion criteria. Basic information was
extracted from each study, including publication year, the       Characteristics of the Population and Quality
name of the first author, language, study design, RAS type,      Assessment
and NLR level.                                                   In total, 13 articles, including 1239 patients with RAS and
                                                                 1167 healthy controls, were included in the analysis [16-28].
Quality Assessment and Study Stratification                      Eleven of them were written in English [16,17,19-27], one in
Numerous methods exist for evaluating observational stud-        Arabic [28] and one in Turkish [18]. There were seven retro-
ies, but the most efficient one is the Newcastle-Ottawa Scale    spective studies [16-18,21,25-27] and six prospective studies
(NOS); hence, this scale was used to evaluate the included       [19,20,22-24,28]. All of them were conducted in Turkey ex-
studies. NOS comprises of three components: selection, com-      cept for one study which was conducted in Syria [28]. Table 1
parability, and exposure, with each having eight entries. This   shows the overall characteristics of the included articles. The
is a semi-quantitative scale, and a score ranging from 0-9       quality assessment revealed that all the studies were of mod-
stars is assigned to each study.                                 erate to high quality based on the NOS scale (Table 1).


Statistical Analysis                                             Differences in NLR Level Between Patients
To compare the two groups, Standardized Mean D
                                             ­ ifference         With RAS and Healthy Controls
(SMD) and 95% Confidence Interval (CI) were used.                A random-effect model revealed that NLR was higher
Statistical heterogeneity was assessed through the Chi-
­                                                                among patients with RAS compared to healthy controls
squared test, and P < 0.10 was considered significant. Quan-     (Figure 2). However, the GRADE approach determined that
titative ­estimation of heterogeneity was based on I2, which     the certainty of this summary estimate of effect was very low
                                        2
ranged from 0% to 100%, where I = 0–25% indicated                (Table 2).
no or mild heterogeneity; I2 = 25–50% indicated moderate            Our subgroup analysis, based on study design, revealed
                 2
­heterogeneity; I = 50–75% indicated large heterogeneity,        that patients with RAS had a higher NLR compared to
and I2 = 75–100% indicated extreme heterogeneity. If I2          healthy controls in retrospective studies, but not in prospec-
­exceeded 50%, a random effects model was used, and if it        tive studies, as shown in Figure 2. In our second subgroup
was less than 50%, a fixed effect model was used.                analysis, based on the NOS score, we found that studies with



Review | Dermatol Pract Concept. 2024;14(1):e2024046                                                                           3
Figure 1. PRISMA 2020 flow diagram for new systematic reviews which includes searches of databases, registers and other sources.



                                 Table 1. General characteristics of included studies.
                                                 Timing of                                                          Healthy
                                                 exposure-                                       RAS group          controls
     First                                       outcome                         Type of                                           NOS
    author    Year Country        Design        measurement       Language         RAS       N        NLR       N       NLR        score
Ozler23       2014 Turkey     Prospective     Simultaneously      English      ND             35   2.05±0.63    35 1.34±0.48        7
Sereflican24 2016 Turkey      Prospective     Simultaneously      English      ND             39   2.12±0.65    34 2.26±1.02        7
Terzi25       2016 Turkey     Retrospective   Simultaneously      English      ND             80   3.37±1.74    80 1.95±1.21        6
Kara18        2017 Turkey     Retrospective   Simultaneously      Turkish      ND            306   1.88±1.00   300 1.83±0.73        8
Kule22        2018 Turkey     Prospective     Simultaneously      English      minor         143   2.25±1.07   134 1.85±0.64        8
Amoun28       2019 Syria      Prospective     Simultaneously      Arabic       ND             40   2.18±0.66    40 1.80±0.42        7
Kayabasi21    2019 Turkey     Retrospective   Simultaneously      English      ND             72   2.60±0.48    60 1.80±0.43        7
Uluyol27      2019 Turkey     Retrospective   Simultaneously      English      Minor or       61   2.61±1.57    40 2.70±0.96        6
                                                                               major
Avci17        2020 Turkey     Retrospective   Simultaneously      English      Minor or       51   1.94±0.74    51 1.80±0.80        7
                                                                               major
Karaer19      2020 Turkey     Prospective     Simultaneously      English      Minor         137   1.90±0.82   137 1.63±0.67        8
         20
Ozden         2021 Turkey     Prospective     Simultaneously      English      Minor,         81   1.95±1.03    69 2.38±1.27        8
                                                                               major, or
                                                                               herpetiform
Turan26       2021 Turkey     Retrospective   Simultaneously      English      ND             97   1.96±0.73    90 1.71±0.65        7
Atalay16      2022 Turkey     Retrospective   simultaneously      English      ND             97   2.66±1.10    97 1.70±0.49        7

ND = not declared; NLR = neutrophil to lymphocyte ratio; NOS = Newcastle-Ottawa scale; RAS = recurrent aphthous stomatitis;.



a score of seven had higher NLR among patients with RAS                     Our fourth subgroup analysis, based on sample size,
compared to healthy controls, but studies with a score of            showed that studies with a large sample size found higher
six or eight did not show such a difference, as depicted in          NLR among patients with RAS in comparison to healthy
Figure 3.                                                            controls, while studies with a small sample size did not show
    Then, we analyzed the data of studies with minor RAS             a significant difference, as illustrated in Figure 5. Lastly, in
and mixed RAS, separately. The difference was not signifi-           the final subgroup analysis based on article language, we
cant in either subgroup (Figure 4).                                  observed that NLR was higher among patients with RAS



4                                                                                 Review | Dermatol Pract Concept. 2024;14(1):e2024046
Figure 2. Meta-analysis of differences in neutrophil to lymphocyte ratio level between patients with recurrent aphthous stomatitis and
healthy controls.



      Table 2. GRADE Evidence Profile for Studies on the Role of lymphocyte ratio level in recurrent
                                         aphthous stomatitis.
                             Risk                                            Publi-
  No of        Study          of                   Indirect- Impre-          cation      Partici-   Cases,
 studies       design        bias    Inconsistency   ness     cision          bias      pants, N      N
 13        observational not     very serious          not         not     very           2406        1239    ⊕○○○        CRITI-
           studies       serious                       serious     serious serious                            Very low    CAL



compared to healthy controls in studies published in English,        provides insight into the interplay between the innate and
but not in studies published in other languages, as indicated        adaptive immune responses. Neutrophils are primary com-
in Figure 6.                                                         ponents of the innate immune system which forms the ba-
                                                                     sis of pro-inflammatory processes [29] and lymphocytes are
Publication Bias                                                     central to the adaptive immune system, serving a predom-
As depicted in Figure 7, our analysis did not reveal any sig-        inantly regulatory function [30]. The NLR thus provides
nificant publication bias among the studies that were in-            insight into the balance between the innate and adaptive im-
cluded (with an Egger test P-value of 0.37 and a Begg test           mune system. Higher NLR values are thought to indicate a
P-value of 0.58).                                                    more severe inflammatory state and suggest worse prognosis
                                                                     in a variety of pathologic states, including those related to in-

Conclusions                                                          flammation, injury, surgery, and cancer [13]. Applying these
                                                                     concepts to recurrent aphthous stomatitis (RAS), the NLR
The NLR, a measure of the ratio between neutrophils and              may suggest that there is a subclinical inflammatory process
lymphocytes, is a marker for inflammation and stress that            present in these patients.



Review | Dermatol Pract Concept. 2024;14(1):e2024046                                                                                5
    Figure 3. Subgroup analysis of the differences in neutrophil to lymphocyte ratio level between patients with recurrent aphthous
    stomatitis and healthy controls, according to Newcastle-Ottawa Scale score.




    Figure 4. Subgroup analysis of the differences in neutrophil to lymphocyte ratio level between patients with recurrent aphthous
    stomatitis (RAS) and healthy controls, according to the type of RAS.



6                                                                                 Review | Dermatol Pract Concept. 2024;14(1):e2024046
      Figure 5. Subgroup analysis of the differences in neutrophil to lymphocyte ratio level between patients with recurrent aphthous
      stomatitis and healthy controls, according to sample size.




      Figure 6. Subgroup analysis of the differences in neutrophil to lymphocyte ratio level between patients with recurrent aphthous
      stomatitis and healthy controls, according to the article language.



Review | Dermatol Pract Concept. 2024;14(1):e2024046                                                                                    7
                       Figure 7. Funnel plot assessing publication bias.




    Although the etiology of RAS is not fully elucidated in            portend diagnostic significance, as well as further elucidate
the literature, immunologic mechanisms are thought to play             pathophysiology of disease. These findings contribute posi-
a central role in its pathologic cascade, making the NLR a             tively to the literature in that they help to discern the immu-
useful tool in helping to understand and decipher the role of          nologic elements at play for patients with RAS, and taking
different immunologic elements in the disease p
                                              ­ rocess [3,31].         into account the diseases relationship to other systemic
Strong evidence for immunologic underpinnings of the dis-              inflammatory diseases, it may play a role in further delin-
ease is based on histopathologic findings showing that                 eating pathologic immune mechanisms of some devastating
aphthous ulcers of RAS patients are characterized by                   disease states previously referenced. Furthermore, our results
cell-mediated inflammation, largely neutrophilic, monocytic            indicate that there may be a relative neutrophilia present in
and T cell infiltration [6,7]. The neutrophilic cells in RAS           patients with RAS compared to controls, allowing for us to
patients have been shown to have increased production of               pinpoint further disturbances in the immunologic mecha-
reactive oxidative species, demonstrating a dysregulated im-           nism of this disease process. With further investigation, this
mune response in these patients. This is further supported             could present numerous applications in the future from a
by the association of RAS with systemic inflammatory dis-              multitude of standpoints including genetics, immunology,
eases such as inflammatory bowel disease, HIV and Behçet               pharmacology, cellular and molecular biology, etc.
disease. Systemically, RAS patients exhibit a heightened                   Nonetheless, it is important to note that additional fac-
pro-inflammatory state, with elevations in cytokines and al-           tors may be contributing to our findings. An example of
tered leukocyte activities – for example, reduced activity of          this would be the known association between psychologi-
regulatory and anti-inflammatory mediators [32].                       cal stressors and RAS [33-35]. RAS patients who experience
    Keeping in mind these major principles from the litera-            anxiety exhibit increased mean salivary cortisol levels [36].
ture, our study evaluated the diagnostic utility of NLR by             Elevated cortisol leads to both neutrophilia and lymphope-
measuring the difference in NLR values between those who               nia and may artificially elevate NLR values found in these
were diagnosed with RAS versus those who were not. Our                 patients. Ultimately, such immunologic perturbations may
study included a total of 1239 patients with RAS and 1167              precipitate RAS flares [37,38]. Another example of factors
healthy controls across a total of 13 studies. The results of          contributing to our findings could be the presence of other
the meta-analysis demonstrate a higher NLR in patients with            inflammatory diseases in patients with RAS. There have been
RAS as compared to those without RAS, indicated by a SMD               numerous studies and reports of comorbid systemic inflam-
of 0.50. The SMD of 0.50 is a standardized measure of the              matory diseases in patients with RAS and such inflammatory
mean difference of NLR values between individuals with                 conditions may inherently produce elevated or altered NLR
RAS as compared to those without and equates to a mod-                 values. With a sample size of more than 1200 patients, this
erate effect size. Altogether, our results suggest that patients       could present a variable influencing our results, especially
with RAS have elevated NLR values and such findings may                given that patients who have evidence of RAS have a higher



8                                                                                 Review | Dermatol Pract Concept. 2024;14(1):e2024046
incidence of inflammatory diseases. Other factors that could      search process ensuring thorough review of the literature.
be influencing our results include laboratory error, inade-       Furthermore, based on the Begg and Egger test, assessment
quate samples, and inconsistencies amongst the included           of publication bias showed no significant bias, further
studies, as will be discussed in our limitations. There is a      strengthening validity of our results. However, our results
plethora of factors within each of the individual studies that    yielded significant heterogeneity for the overall pooled re-
could be contributing to our overall result, and the limita-      sults with an overall I2 value of 91.5%, thus limiting gener-
tions of each study are not to be ignored when considering        alizability of our findings. We speculated that study design
the utility of our results. Future studies that control for the   could be contributing to heterogeneity and to further ex-
presence of stress and anxiety when evaluating NLR values         plore this, subgroup analysis was completed. However, such
in RAS patients, and studies that focus on eliminating other      stratification did not appear to explain heterogeneity. Thus,
confounding variables are necessary for gaining a better          we speculated additional factors contributing to heteroge-
understanding of our results in the setting of RAS. Finally,      neity may include variations in RAS diagnosis, study pop-
across the studies in our meta-analysis, hematologic values       ulations, and geographic location of studies. For example,
and RAS diagnosis were obtained simultaneously. Thus, we          baseline NLR values appear to vary by geographic location
cannot delineate cause and effect but, rather, can only state     and race [13,40]. Such variations may suggest inherent dif-
the presence of a correlation between the presence of RAS         ferences in the degree to which NLR responds to pathologic
and elevated NLR values. As such, we cannot determine if          insults among different populations and could introduce fur-
elevated NLR values precipitate disease or, alternatively, are    ther heterogeneity.
an end-result of the disease process. Future studies evaluat-        Moreover, on subgroup analysis by study design, there
ing NLR values before and after RAS flares could help to          was a loss of effect size for prospective studies. The reason
answer this important question.                                   for this is not clear and should be investigated further. In
   Another important implication of our findings lies in the      particular, retrospective studies are subject to a greater risk
diagnostic significance of our results. Currently, the diagno-    of bias, and it is unclear if the retained effect size in ret-
sis of RAS is largely clinical without an objective quantita-     rospective studies is a result of such. Therefore, additional
tive measure. A quantitative diagnostic value, as an adjunct      prospective studies, perhaps with standardized protocols,
to clinical presentation, may enable more efficient diagnosis     will be needed to better characterize the associations of
of new and recurrent disease. Further, and perhaps of greater     NLR values with RAS, and to clarify prognostic utility. In
significance, NLR values may also serve to characterize dis-      addition, the protocol of our systematic review had not been
ease severity in these patients to ultimately guide therapeutic   pre-registered (eg in PROSPERO). This is a concern as it
management. To explain, currently, treatment of RAS in-           introduces potential bias to the review and does not align
volves a stepwise approach, with choice of anti-inflammatory      with Cochrane guidance. Finally, the sample size (N = 13)
agents escalated based on symptom severity and therapeutic        for our study is relatively small and may further limit greater
response. However, many commonly used agents are not ef-          generalization of results. As additional studies are published
fective for all patients and targeted treatment remains a chal-   on the matter, future meta-analysis with greater sample sizes
lenge. In this context, two prior studies have found that NLR     and power will be useful to confirm the findings of our study.
measurements correlate with disease severity. Thus, NLR val-         RAS is a highly prevalent disorder with a poorly under-
ues may help to define severity of disease to guide selection     stood pathogenesis, an imprecise method of treatment, and a
of more appropriate anti-inflammatory agents while early in       measurable impact on patient quality of life. Despite unclear
disease course. However, there remains inconsistencies in the     etiology, much research has supported a role of immune
literature in regard to NLR correlation with RAS severity.        dysregulation in disease pathogenesis. In this systematic re-
For example, a study by Kayabasi and colleagues found no          view and meta-analysis, we found NLR values to be signifi-
significant differences in NLR values among RAS patients          cantly greater in patients with RAS as compared to those
with active and inactive disease, suggesting absence of cor-      without, further supporting an immunologic mechanism of
relation with disease severity [39]. Therefore, further studies   disease. In addition, our results suggest diagnostic utility of
are needed to clarify this important correlation in order to      NLR values in RAS patients. Further, reports of correlations
more confidently determine the role of NLR in guiding treat-      between elevated NLR values and disease activity support
ment decisions. Nonetheless, the potential diagnostic signifi-    potential prognostic utility of NLR. However, due to small
cance of NLR values remains. In summary, NLR is a readily         sample size and lack of effect size when stratifying by study
available and affordable hematologic value that may serve as      design, further prospective studies will be needed to clarify
an objective adjunctive tool to better diagnose disease.          associations found in this study and to further explore prog-
   Our study has both strengths and limitations. Fore-            nostic utility. Nonetheless, based on the results of our study,
most, this meta-analysis was conducted using a methodical         NLR is a practical marker of inflammation which shows an



Review | Dermatol Pract Concept. 2024;14(1):e2024046                                                                           9
association with RAS and holds potential to further eluci-                14. Page MJ, McKenzie JE, Bossuyt PM, et al. The PRISMA 2020
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Review | Dermatol Pract Concept. 2024;14(1):e2024046                                                                                    11
