FRESH HEMOLYSIS INTERFERES WITH BLOCKED P-NITROPHENYLMALTOHEPATAOSIDEAMYLASE METHODS

Two commercial amylase methods which employ p-nitrophenol derivatives of blocked maltoheptaosides suffer from negative interference due to f resh haemolysate. Specimen storage at room temperature, or pre-incubat ion at 37-degrees-C or 57-degrees-C removes the effect. Incubation of amylase reagent at 37-degrees-C with fresh haemolysate where the final haemoglobin concentration was 0.011 g/L, showed a rapid fall in absor ption around 414 nm which became stable after 150 min. Since p-nitroph enol, the product of the amylase reaction, is measured at 405 nm it is concluded that the negative interference from fresh haemolysis is due to the transitory fall in absorption around 405 nm. It is recommended that amylase measurements using this technique, particularly those pe rformed as an emergency, should not be done on haemolysed specimens.