Influence of Amylase Assay Technique on Renal Clearance of Amylase-Creatinine Ratio

The influence of amylase assay technique on the renal amylase/creatinine clearance measurement was determined by analysis of serum and urine specimens obtained from 10 normal subjects. C_AM/C_Cr averaged 2.19 ± 0.18% with a saccharogenic technique, 1.52 ± 0.2% with an iodometric technique, and 0.80 -t 0.08% with a chromogenic technique. Each of these values differed significantly (P < 0.05) from the other two. Recovery studies were carried out by adding partially purified human salivary or pancreatic amylase to human newborn serum or urine (which contain minimal endogenous amylase). Equal amylase activity was recovered from serum and urine by the saccharogenic technique whereas recovery from urine was less than 50% of that from serum using the iodometric and chromogenic techniques. The accuracy of the chromogenic technique is markedly improved by the addition of albumin to the urine assay system. Although it appears that only the saccharogenic method provides an accurate estimate of C_AM/C_Cr, each assay technique distinguished the elevated C_AM/C_Cr, of patients with pancreatitis from the normal range established for that technique. Accurate clinical interpretation of CAM/CC, measurement requires knowledge of the amylase assay technique used.