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Laboratory Vignette Style

For testing of general principles and concepts not specific to a single patient, then a vignette presenting data in the manner of a scientific study or experiment may be most appropriate. Such questions are often based upon studies that have actually been done. Such questions test application of knowledge, not just memorization.

Examples of Lab Vignettes

A 200 mg dose of Drug X is administered by intravenous injection to a healthy 25-year-old man who weighs 70 kg. The peak plasma concentration of the unbound Drug X is 5 mg/L. Drug X is most likely distributed into which of the following volumes?

A. Cerebrospinal fluid

B. Extracellular compartment

C. Intracellular compartment

D. Plasma

E. Total body water

In this example the format is completely experimental, since the name of an actual drug is not given, so that just the concept of volume of distribution is tested. The answer here is foil E.

A bacterium isolated from a urine culture grows on blood agar aerobically. It is found to be gram negative. On antimicrobial sensitivity testing it is found to be resistant to multiple antibiotic drugs. This resistance is most likely related to presence of which of the following bacterial structural components?

A. Flagellum

B. Lipopolysaccharide

C. Peptidoglycan

D. Pilus

E. Plasmid

In this example the construct of bacterial structure and function is tested, with identification of plasmids (foil E) as the driving force behind much antibiotic resistance. The other foils have to do with other bacterial properties related to infection, but not to resistance.

In an experiment, a normal healthy 20-year-old woman drinks a liter of water in one minute. After 30 minutes the following measurements are obtained:
Urine flow 10 mL/min
Urine osmolality 150 mOsm/L
Plasma osmolality 300 mOsm/L
What is her free water clearance?

A. 5 mL/min

B. 10 mL/min

C. 15 mL/min

D. 20 mL/min

E. 30 mL/min

Here is an example of data in a tabular format, which helps to speed the reading and comprehension of the data. It is often possible to get the answer without actually performing the calculations. The only viable answer here is foil A for a normal person.

Phonographic and electrocardiographic recordings are made from a trained adult athlete's heart and shown in the figure:
At which point would the second heart sound on auscultation most likely be heard?

A. Point A

B. Point B

C. Point C

D. Point D

The scenario of an athlete is used here to justify the presence of the 3rd and 4th heart sounds in the graphical display. The answer here is foil C.

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