NRCMA Laboratory Procedures 2 — Questions and Answers

Question 1: The order of draw for venipuncture using evacuated tubes begins with:

EDTA (lavender) tube
Blood culture bottles (Correct answer)
SST (gold/red) tube
Sodium citrate (light blue) tube

Correct answer: Blood culture bottles

Blood culture bottles are drawn first to prevent contamination from tube additives. CLSI order: blood cultures → light blue → red/gold → green → lavender → gray.

CLSI order of draw: (1) Blood cultures, (2) Light blue (coagulation), (3) Red or SST gold (serum), (4) Green (heparin), (5) Lavender (EDTA), (6) Gray (fluoride/oxalate). Incorrect order causes additive carryover, falsely altering analyte values — for example, EDTA potassium contaminating a heparin tube causes falsely elevated K+ results.

Question 2: When performing a finger-stick capillary blood collection, the best site on an adult is:

The center pad of the fingertip
The lateral tip of the ring or middle finger (Correct answer)
The index finger tip center
The thumb tip

Correct answer: The lateral tip of the ring or middle finger

The lateral side of the ring or middle finger has adequate capillary blood flow, less nerve density, and avoids the sensitive fingertip center, minimizing discomfort.

CLSI recommends puncturing the palmar surface of the distal segment of the middle or ring finger, slightly off-center toward the lateral aspect. Avoid the thumb (arterial pulse), index finger (more nerve endings), pinky (small volume), and finger center (pain, bone proximity). Wipe away the first drop to eliminate tissue fluid contamination. Heel sticks are used for neonates.

Question 3: A point-of-care (POC) INR test would be ordered to monitor therapy with which medication?

Metformin
Warfarin (Coumadin) (Correct answer)
Lisinopril
Atorvastatin

Correct answer: Warfarin (Coumadin)

INR (International Normalized Ratio) measures standardized prothrombin time and is used to monitor warfarin anticoagulation therapy.

Warfarin inhibits vitamin K-dependent clotting factors II, VII, IX, X, and proteins C and S. Therapeutic INR ranges: atrial fibrillation/VTE 2.0–3.0; mechanical heart valves 2.5–3.5. Sub-therapeutic INR: clot risk. Supra-therapeutic INR: bleeding risk. POC INR devices allow clinic-based or patient self-monitoring without a full coagulation lab.

Question 4: The Gram stain procedure classifies bacteria based on:

Their oxygen requirements (aerobic vs anaerobic)
Cell wall composition — gram-positive retain crystal violet; gram-negative do not (Correct answer)
Spore formation
Capsule presence

Correct answer: Cell wall composition — gram-positive retain crystal violet; gram-negative do not

Gram-positive bacteria have thick peptidoglycan walls that retain crystal violet and appear purple. Gram-negative bacteria have thin peptidoglycan and appear pink/red after the safranin counterstain.

Gram stain steps: (1) Crystal violet — all cells purple, (2) Iodine mordant — fixes dye, (3) Alcohol decolorizer — removes dye from gram-negative, (4) Safranin counterstain — gram-negative turns pink. Gram-positive examples: Staphylococcus, Streptococcus. Gram-negative examples: E. coli, Neisseria, Pseudomonas. This guides empiric antibiotic selection before culture results return.

Question 5: Which condition is indicated by a urine specific gravity of 1.035?

Overhydration / dilute urine
Diabetes insipidus
Concentrated urine / possible dehydration (Correct answer)
Normal hydration

Correct answer: Concentrated urine / possible dehydration

Normal urine specific gravity is 1.005–1.030. A value of 1.035 indicates highly concentrated urine, suggesting dehydration or inadequate fluid intake.

Urine specific gravity measures solute concentration relative to water (1.000). Values below 1.005 indicate overhydration or diabetes insipidus. Values above 1.030 suggest dehydration or SIADH. The refractometer is the most accurate CLIA-waived POC instrument for measuring specific gravity.

Question 6: The term 'CLIA-waived' for a laboratory test means:

The test is not approved by the FDA
The test is simple, accurate, and poses minimal patient risk — and can be performed without complex lab certification (Correct answer)
The test requires a CLIA certificate of accreditation
Only physicians may perform the test

Correct answer: The test is simple, accurate, and poses minimal patient risk — and can be performed without complex lab certification

CLIA-waived tests are FDA-cleared, simple to perform, and have a low risk of error. Medical assistants can perform them in physician office labs with a certificate of waiver.

CLIA categorizes lab tests: Waived (simple, minimal error risk — dipstick urinalysis, fingerstick glucose, rapid strep, flu, pregnancy tests), Moderate complexity (most routine lab tests), High complexity (cytogenetics, some microbiology). A Certificate of Waiver requires bi-annual renewal and allows offices to perform only waived tests.

NRCMA Laboratory Procedures 2

The order of draw for venipuncture using evacuated tubes begins with: