CLS Cheat Sheet 2026

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

1. What is the fundamental principle of the ELISA (Enzyme-Linked Immunosorbent Assay)? → Enzyme-conjugated antibodies generate a measurable color change upon antigen binding
2. Sickle cell disease results from a mutation in which protein? → Hemoglobin
3. What quality assurance measure supports continuing education requirements? → Regular self-assessment, peer review, and adherence to established standards
4. How should challenges in assessment and evaluation be addressed? → Apply systematic problem-solving, seek expert guidance when needed, and document decisions
5. Which immunoglobulin class is the predominant antibody in mucosal secretions such as saliva, tears, colostrum, and breast milk? → Secretory IgA (sIgA)
6. Which electrolyte abnormality is most likely to cause prolonged QT interval and potentially fatal cardiac arrhythmias? → Hypomagnesemia
7. What is the final step in the laboratory testing process? → Documenting and reporting results
8. Which symbol indicates a biohazard in the laboratory? → Three-ring biohazard symbol
9. What ethical standard governs assessment and evaluation practice? → Adherence to the profession's code of ethics and applicable laws and regulations
10. Which type of anemia presents with macrocytic red cells and hypersegmented neutrophils (≥5 lobes) on peripheral smear? → Megaloblastic anemia
11. Which thyroid function test is considered the most sensitive initial screening test for thyroid disorders? → Thyroid-stimulating hormone (TSH)
12. Why are proficiency testing programs important? → They help verify lab accuracy by external comparison
13. What is PCR primarily used for in diagnostics? → Amplifying genetic material
14. What is the normal reference range for hemoglobin in adult males? → 13.5–17.5 g/dL
15. How should challenges in safety and compliance be addressed? → Apply systematic problem-solving, seek expert guidance when needed, and document decisions
16. Which blood cell type is primarily responsible for oxygen transport? → Erythrocytes
17. What ethical standard governs industry best practices practice? → Adherence to the profession's code of ethics and applicable laws and regulations
18. Target cells (codocytes) on a peripheral smear are most associated with which conditions? → Iron deficiency anemia, liver disease, and hemoglobin C disease
19. What quality assurance measure supports assessment and evaluation? → Regular self-assessment, peer review, and adherence to established standards
20. Which protein is measured to assess long-term glycemic control over approximately 2-3 months? → Glycated hemoglobin (HbA1c)
21. Which test is used as the CONFIRMATORY test for HIV after a positive 4th-generation ELISA/immunoassay screen? → Western blot / HIV-1/2 differentiation immunoassay
22. What does Mean Platelet Volume (MPV) measure on a CBC? → Average platelet size
23. Which instrument is commonly used to separate blood components? → Centrifuge
24. How often should quality control be performed? → With each test run or daily
25. Which antibody class is the FIRST produced during a primary immune response? → IgM
26. What quality assurance measure supports professional standards and ethics? → Regular self-assessment, peer review, and adherence to established standards
27. The Quellung (capsular swelling) reaction uses type-specific antisera to identify which encapsulated organism? → Streptococcus pneumoniae
28. Hemolytic Uremic Syndrome (HUS) is classically characterized by which triad? → Microangiopathic hemolytic anemia, thrombocytopenia, and acute renal failure
29. What is the main purpose of quality control in a laboratory? → To monitor and maintain test result accuracy
30. Beta-lactamase-producing organisms are resistant to which antibiotic class? → Beta-lactams (penicillins/cephalosporins)