MLS Cheat Sheet 2026

The 30 highest-yield MLS facts, distilled from real exam questions. Print it, save it as a PDF, or study it here — free, no sign-up.

1. Which laboratory test is used to MONITOR patients receiving thiopurine therapy (azathioprine or 6-mercaptopurine) for inflammatory bowel disease? → Thiopurine methyltransferase (TPMT) activity and thiopurine metabolite levels
2. An MLS receives a specimen labeled only with a room number and no patient identifiers. The correct action is to: → Reject the specimen and request a properly labeled recollection
3. A patient with Type A blood has which naturally occurring antibody in their serum? → Anti-B
4. A sputum Gram stain shows >25 squamous epithelial cells per low-power field. The laboratory should: → Report the specimen as unsatisfactory and request a new sample
5. What does informed consent require in Medical Laboratory Scientist practice? → Full disclosure of relevant information before obtaining agreement
6. When an MLS identifies a potential pre-analytical error that may have affected a reported result, the most appropriate action is to: → Immediately notify the supervisor and the clinical team, and document the concern
7. A Neubauer hemocytometer counting chamber has a depth of: → 0.1 mm
8. In flow cytometry, which parameter is used to measure cell size? → Forward scatter (FSC)
9. In the laboratory chain of custody, documentation is critical primarily to: → Ensure specimen integrity and legal defensibility of results
10. A stool culture grows Salmonella typhi. Besides the clinical team, this result must be reported to: → Public health authorities, as it is a reportable pathogen
11. When using a refractometer to measure urine specific gravity, the instrument measures: → The refractive index, which correlates with solute concentration
12. Which of the following organisms requires both an alkaline (pH 8.6) peptone water enrichment and TCBS agar for optimal isolation from stool? → Vibrio cholerae
13. Which laboratory test is used to assess coagulation function? → Prothrombin Time (PT)
14. A laboratory receives a blood culture bottle that has been incubating for 5 days with no growth signal. What is the standard reporting outcome? → Report 'No growth at 5 days' and discard
15. Which of the following tests is most commonly used to assess kidney function in a clinical laboratory? → Creatinine
16. Which piece of laboratory equipment is used to measure the absorbance of a solution at a specific wavelength? → Spectrophotometer
17. In urinalysis, a positive nitrite test indicates the presence of: → Gram-negative bacteria that reduce nitrate to nitrite
18. The purpose of the eyewash station in the laboratory is to flush chemicals from the eyes for a minimum of: → 15 minutes
19. What is the purpose of running a blank in photometric assays? → To zero the instrument and eliminate background absorbance
20. Which of the following is a critical component of a laboratory’s quality assurance (QA) program? → Proficiency testing
21. A patient's serum creatinine is 1.1 mg/dL. The estimated GFR (eGFR) calculated using the CKD-EPI equation is 68 mL/min/1.73m². This result best reflects: → Mildly decreased kidney function (eGFR 60–89)
22. A laboratory scientist discovers a mercury thermometer has broken and spilled in the chemistry section. The correct response is to: → Evacuate the area and use a mercury spill kit according to policy
23. Which laboratory finding would prompt a clinician to SWITCH from oral to IV vancomycin when treating Clostridioides difficile (C. diff) infection? → Evidence of ileus or toxic megacolon on imaging
24. What is the primary function of a fume hood in a laboratory? → Protect users from harmful fumes
25. Which blood type is the universal recipient for packed red blood cells? → AB positive
26. What is the primary purpose of quality control (QC) in a clinical laboratory? → To ensure accuracy and reliability
27. Which Rh antigen is considered the most clinically significant and immunogenic? → Rh D
28. A random urine albumin-to-creatinine ratio (ACR) of 45 mg/g in a diabetic patient indicates: → Moderately increased albuminuria (microalbuminuria)
29. Which test is most appropriate for diagnosing diabetes mellitus? → Hemoglobin A1c
30. A laboratory scientist is working with a patient specimen that may contain Coccidioides immitis. Which containment practice is MOST critical? → Perform all manipulations in a Class II BSC to prevent aerosol exposure