Interferences with the starch-iodine assay for serum amylase activity, and effects of hyperlipemia

Recent reports imply or claim that amylase activity is inhibited in hyperlipemic sera, because diluted samples showed greater activities when assayed by a starch-iodine method. We find that dilutions of both clear and lipemic samples give higher-than-expected activities when assayed by a starch-iodine method, an effect attributable to the variable effects of protein, turbidity, and triglycerides in the hyperlipemic samples. Thus the starch-iodine method is unsuitable for assessing the effects of hyperlipemic samples on amylase activity. To do so, we used an alternative method, in which soluble dyed amylopectin is used as the substrate. This method exhibits apparent zero-order kinetics, and we detected no interfering factors. Plots of sample volume (x) vs. activity (y) for clear and hyperlipemic (triglycerides up to 80 g/liter) sera gave straight lines with y-intercepts of zero. Evidently hypertriglyceridemia does not inhibit amylase activity.