Isoamylase measurements with monoclonal antibody test strips

A test strip with fixed monoclonal antibodies binding human salivary amylase (5) was used for the measurement of pancreatic amylase in human sera. The amount of salivary isoamylase adsorbed by the test strip increased with the amount of enzyme in the test solution, reaching a maximum absorption capacity of 620 mU at a test quantity of 900 mU. At about 160 U/l of pancreatic isoamylase (in a mixture containing 214 U/l of total alpha-amylase, both enzymes with 4-nitrophenyl-alpha-D-maltoheptaoside at 25 degrees C) imprecision within-run (and day-to-day) was 2.8% (and 6.8%) at this level of clinical importance. The preliminary 95%-reference interval from 33 healthy adults was calculated to be 16.6-44.2 U/l. The method proved valuable for the interpretation of slightly elevated alpha-amylase levels (up to twice the upper reference limit) and unusual lipase/amylase ratios.