Laboratory Science Cheat Sheet 2026

The 30 highest-yield Laboratory Science 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 order of blood tube draw for multiple specimens (correct order of draw)? → Citrate → SST/Gold → Heparin → EDTA
2. Which urine cast type indicates the most severe renal tubular damage? → Waxy (broad) casts
3. Which agency regulates the transport of infectious substances in the United States? → DOT (Department of Transportation)
4. What class of fire extinguisher is appropriate for a chemical laboratory fire involving flammable liquids? → Class B
5. What does a urine specific gravity of 1.001 suggest? → Very dilute urine, possibly from excessive water intake or diabetes insipidus
6. What is the purpose of a fume hood in a laboratory? → To contain and exhaust hazardous vapors away from lab personnel
7. What is the significance of urobilinogen in urine? → Reflects enterohepatic circulation of bilirubin; elevated in hemolysis or hepatic disease
8. What does SDS stand for in laboratory chemical safety? → Safety Data Sheet
9. The weak D test is performed primarily to: → Detect weak expression of the D antigen in apparently Rh-negative individuals
10. Which biosafety level (BSL) is required for working with agents that pose a moderate risk to personnel but low risk to the community? → BSL-2
11. Which pancreatic enzyme is elevated in acute pancreatitis and peaks within 24 hours of onset? → Amylase (rises faster but falls sooner)
12. What is the clinical significance of a positive urine leukocyte esterase test? → Suggests WBCs are present, indicative of urinary tract infection or inflammation
13. At what temperature should packed red blood cell units be stored? → 1-6°C
14. A differential WBC count showing 85% neutrophils in an adult patient most likely suggests which condition? → Bacterial infection
15. What does the osmolal gap indicate when elevated? → Presence of unmeasured osmoles such as ethanol, methanol, or ethylene glycol
16. Which enzyme is the primary cardiac biomarker used to diagnose acute myocardial infarction? → Troponin I or T
17. What is the significance of a 'satellite phenomenon' around Staphylococcus aureus on blood agar? → Suggests Haemophilus influenzae growth due to V-factor (NAD) provision
18. Which stain is routinely used to differentiate white blood cell types on a peripheral blood smear? → Wright-Giemsa stain
19. Ketones in urine (ketonuria) are most commonly seen in which metabolic state? → Diabetic ketoacidosis (DKA) or starvation/fasting
20. When using a centrifuge, what is the most important safety precaution? → Balance opposing tubes with equal mass
21. Blood cultures are typically incubated for how many days before being reported as negative? → 5 days
22. Which Rh antigen is the most clinically significant and is the basis for Rh-positive/Rh-negative typing? → D antigen
23. Which CD marker is used to identify T helper lymphocytes, and its count monitors HIV/AIDS progression? → CD4
24. Which organism produces a characteristic 'school of fish' arrangement on gram stain? → Corynebacterium diphtheriae
25. Which tube color is used for coagulation studies (PT/aPTT) in the US? → Light blue/sodium citrate
26. What does a positive catalase test (bubbling with H₂O₂) indicate? → The organism produces catalase enzyme, suggesting Staphylococcus (not Streptococcus)
27. Which cell type predominates in viral meningitis CSF analysis? → Lymphocytes
28. Which culture medium is used for isolating Neisseria gonorrhoeae from clinical specimens? → Thayer-Martin (modified) agar
29. What is the primary purpose of the antibody screen in pre-transfusion testing? → Detect clinically significant unexpected antibodies in patient serum
30. What does the term 'universal precautions' mean in a laboratory setting? → Treat all blood and body fluids as potentially infectious