Quick Review Cards for Medical Laboratory Science

Calculated Chemistry Valuescontinued Clinical Chemistry Review 129

VALUE CALCULATION NORMAL RANGE CLINICAL SIGNIFICANCE

BUN-to-creatinine
ratio

Creatinine
clearance

Indirect
(unconjugated)
bilirubin

LDL cholesterol

BUN

Creatinine

urine creatinine (mg/dL) × urine mL per 24hr/1,440

plasma creatinine (mg/dL)

× 1.73

body surface area

Total bilirubin – direct (conjugated) bilirubin

Friedewald formula:

LDL-C = total cholesterol − [HDL-C +

(triglycerides/5)]

10–20

M: 97–137 mL/min

F: 88–128 mL/min

<0.2 mg/dL

Desirable level

<130 mg/dL

Normal ratio with renal disease.

Prerenal conditions: ↑ratio with

↑BUN & normal CR. Postrenal

conditions: ↑ratio with ↑CR.

Ratio ↓with ↓urea production

(e.g., severe liver disease, ↓pro-

tein intake).

↓renal disease (early indicator).

↑prehepatic, posthepatic, &

some types of hepatic jaundice.

↑LDL cholesterol associated

with ↑risk of CAD. Not valid if

triglycerides >400 mg/dL. Direct

measurements now available.

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