Calculated Chemistry Values Clinical Chemistry Review 128
VALUE CALCULATION NORMAL RANGE CLINICAL SIGNIFICANCE
A/G ratio
Amylase: creatinine
clearance ratio
Anion gap
Albumin
Total protein − albumin
Urine amylase (U/L) × serum creatinine (mg/L)
Serum amylase (U/L) × urine creatinine (mg/L)
(Na++ K+) – (Cl–+ HCO 3 – )
or
Na+– (Cl–+ HCO 3 – )
1–2.5
2%–5%
10–20
or
7–16
Reversed A/G ratio with multiple
myeloma, liver disease.
↑acute pancreatitis.
↓macroamylasemia.
Difference between unmeasured
anions & unmeasured cations.
↑in renal failure; diabetic acido-
sis; lactic acidosis; methanol,
ethanol, ethylene glycol, or
salicylate poisoning; laboratory
error. Useful QC check. Can’t be
a negative number. If all deter-
minations are ↑or ↓, possible
instrument error in 1 of the
determinations.
continued...
