Laboratory Mathematics and Calculations Flashcards

Urine creatinine is 100 mg/dL, 24-hour urine volume is 1440 mL, and plasma creatinine is 1.0 mg/dL. What is the creatinine clearance?

Answer: 100 mL/min

1440 mL/1440 min = 1 mL/min, so UV/P = (100 × 1)/1.0 = 100 mL/min.

Using the Friedewald equation, what is the calculated LDL for total cholesterol 200 mg/dL, HDL 50 mg/dL, and triglycerides 150 mg/dL?

Answer: 120 mg/dL

LDL = TC − HDL − TG/5 = 200 − 50 − 30 = 120 mg/dL.

Calculate the anion gap: Na+ 140 mmol/L, Cl- 100 mmol/L, HCO3- 24 mmol/L.

Answer: 16 mmol/L

AG = Na − (Cl + HCO3) = 140 − 124 = 16 mmol/L.

Calculate serum osmolality: Na+ 140 mmol/L, glucose 90 mg/dL, BUN 14 mg/dL.

Answer: 290 mOsm/kg

2(140) + 90/18 + 14/2.8 = 280 + 5 + 5 = 290 mOsm/kg.

A patient has a hematocrit of 45% and an RBC count of 5.0 × 10^12/L. What is the MCV?

Answer: 90 fL

MCV = (Hct × 10) / RBC = 450 / 5.0 = 90 fL.

A patient has hemoglobin 15 g/dL and hematocrit 45%. What is the MCHC?

Answer: 33.3 g/dL

MCHC = (Hgb / Hct) × 100 = (15/45) × 100 = 33.3 g/dL.

The automated WBC count is 10,000/µL and 25 nucleated RBCs are seen per 100 WBCs on the differential. What is the corrected WBC count?

Answer: 8,000/µL

Corrected WBC = 10,000 × 100/(100 + 25) = 8,000/µL.