The commercially available ELISA for pancreatic elastase 1 based on polyclonal antibodies does measure an as yet unknown antigen different from purified elastase 1. Binding studies and clinical use in patients with exocrine pancreatic insufficiency.

The measurement of fecal elastase 1 concentrations by means of an ELISA based on monoclonal antibodies (mABs) highly specific for human elastase 1 (ELISA 1) has become an accepted indirect test of the exocrine pancreatic function during the last years. Its use has been demonstrated in many clinical studies including comparison with direct function tests and ERCP morphology. Recently, a new ELISA, also named "elastase 1" based on polyclonal antibodies (pABs; ELISA 2) became available. In the present investigation we performed binding studies with purified elastase 1 as well as studies on patients with exocrine insufficiency with both ELISAs. Surprisingly, the pABs on the solid phase (catcher antibodies) of ELISA 2 did not bind purified elastase 1. These antibodies seem to react with an as yet unknown antigen associated with elastase 1. Measurement of samples from patients suspected to suffer from exocrine insufficiency showed a weak correlation of both assays but higher levels in ELISA 2, resulting in false normal results even in some patients with pancreatic steatorrhea. Since the reference range used in both assays has been established using ELISA 1, ELISA 2 must be re-evaluated in comparison to direct function tests. ELISA 2 should be renamed, since obviously it does react with an antigen (antigens) different from elastase 1.