NRCMA Laboratory Procedures 1 — Questions and Answers

Question 1: A fasting blood glucose level of 126 mg/dL or higher on two separate occasions indicates:

Hypoglycemia
Pre-diabetes (impaired fasting glucose)
Diabetes mellitus (Correct answer)
Normal glucose metabolism

Correct answer: Diabetes mellitus

Per ADA criteria, a fasting blood glucose of 126 mg/dL or higher confirmed on two occasions meets the diagnostic threshold for diabetes mellitus.

ADA diagnostic criteria for diabetes: Fasting plasma glucose ≥126 mg/dL; 2-hour glucose ≥200 mg/dL on OGTT; A1C ≥6.5%; or random glucose ≥200 mg/dL with symptoms. Pre-diabetes: fasting 100–125 mg/dL. Normal fasting: below 100 mg/dL. Hypoglycemia: below 70 mg/dL. Confirmation with a second test is required unless unequivocal hyperglycemia symptoms are present.

Question 2: When collecting a clean-catch midstream urine specimen, the patient should:

Collect the entire void in the cup
Collect only the final portion of the void
Clean the urethral meatus, discard initial flow, then collect midstream (Correct answer)
Use a catheter to obtain the sample

Correct answer: Clean the urethral meatus, discard initial flow, then collect midstream

Clean-catch midstream technique cleans the urethral area, discards the initial stream (which flushes urethral contaminants), then collects midstream urine for accurate culture results.

CCM protocol: (1) Clean meatus with antiseptic wipes front-to-back; (2) Begin voiding, discard first 10–20 mL; (3) Collect 30–60 mL midstream; (4) Complete void in toilet. Collecting the entire void yields false-positive cultures from urethral flora. Specimen must reach the lab within 30 minutes at room temperature or within 2 hours if refrigerated.

Question 3: The hemoglobin A1C test measures:

Immediate blood glucose at time of blood draw
Average blood glucose over the preceding 2–3 months (Correct answer)
Urine glucose concentration
White blood cell response to glucose

Correct answer: Average blood glucose over the preceding 2–3 months

HbA1c reflects the percentage of hemoglobin glycated over the lifespan of red blood cells (~120 days), providing a 2–3 month average blood glucose estimate.

Glucose binds irreversibly to hemoglobin. Since RBCs live ~120 days, A1C reflects average glucose over ~60–90 days. A1C 5.7–6.4% = pre-diabetes; ≥6.5% = diabetes. Therapy target for most diabetics: A1C below 7% (ADA). Conditions affecting RBC lifespan (sickle cell, hemolytic anemia) can falsely alter A1C values.

Question 4: In a complete blood count (CBC), a differential WBC count identifies:

The total number of red blood cells
The percentage and type of each white blood cell in the sample (Correct answer)
Platelet morphology
Hemoglobin and hematocrit values

Correct answer: The percentage and type of each white blood cell in the sample

The differential count classifies leukocytes into five types (neutrophils, lymphocytes, monocytes, eosinophils, basophils) and reports each as a percentage of total WBCs.

Normal adult WBC differential: neutrophils 50–70%, lymphocytes 20–40%, monocytes 3–8%, eosinophils 1–4% (increased in allergies/parasites), basophils 0.5–1%. Left shift indicates increased immature neutrophils (bands), signaling acute infection. Leukocytosis = high WBCs; leukopenia = low WBCs.

Question 5: Which color-coded evacuated tube top is used for coagulation studies (PT/INR, aPTT)?

Red/gold (SST)
Lavender/purple (EDTA)
Light blue (sodium citrate) (Correct answer)
Green (lithium heparin)

Correct answer: Light blue (sodium citrate)

Light blue-top tubes contain sodium citrate anticoagulant and must be filled exactly to the line to maintain the 9:1 blood-to-anticoagulant ratio required for accurate coagulation testing.

Evacuated tube guide: Light blue (sodium citrate) — PT/INR, aPTT, fibrinogen; Red or Gold/SST — serum chemistries; Lavender/purple (EDTA) — CBC, blood bank; Green (heparin) — plasma chemistries; Gray (sodium fluoride) — glucose/lactate; Yellow (SPS) — blood cultures. Correct tube order of draw prevents cross-contamination of additives.

Question 6: A urine dipstick positive for both nitrites and leukocyte esterase most likely indicates:

Renal calculi (kidney stones)
Urinary tract infection (UTI) (Correct answer)
Nephrotic syndrome
Dehydration

Correct answer: Urinary tract infection (UTI)

Nitrites (produced by bacteria converting urinary nitrates) combined with leukocyte esterase (released by WBCs) strongly suggest bacterial urinary tract infection.

Dipstick interpretation: Nitrites positive indicates gram-negative bacteria (E. coli most common UTI pathogen). Leukocyte esterase positive indicates WBCs in urine (pyuria). Both positive yields approximately 85–90% predictive value for UTI; confirm with culture. Kidney stones cause hematuria. Nephrotic syndrome causes proteinuria. Dehydration causes high specific gravity without infection markers.

NRCMA Laboratory Procedures 1

A fasting blood glucose level of 126 mg/dL or higher on two separate occasions indicates: