Solid‐phase extraction treatment is required for measurement of active glucagon‐like peptide‐1 by enzyme‐linked immunosorbent assay kit affected by heterophilic antibodies

AIMS/INTRODUCTION: It is reported that interfering substances in the blood might influence the value for measurement of active glucagon‐like peptide‐1 (GLP‐1) in human plasma. Solid phase extraction (SPE) pretreatment is recommended to reduce their influence, but it requires a lot of cost and time. However, there is little investigation about causative inhibitory substances and about methods that can replace solid phase extraction. In the present study, we aimed to seek the candidate of the substances that might interfere with an active GLP‐1 enzyme‐linked immunosorbent assay (ELISA). MATERIALS AND METHODS: Two kinds of active GLP‐1 ELISA kits using different antibodies, plural extraction carriers and elution solutions were used to evaluate the SPE method. Active GLP‐1 concentration was compared with or without SPE, and with or without a heterophilic blocking tube. RESULTS: Active GLP‐1 values were often higher without SPE compared with those with SPE pretreatment. This difference was eliminated by pretreatment with a heterophilic blocking tube or ELISA kits that did not use a mouse monoclonal antibody, and was independent of SPE. CONCLUSIONS: Substances absorbed to a heterophilic blocking tube carrier might interfere with an active GLP‐1 immunoassay. Solid‐phase extraction treatment is required for measurement of active GLP‐1 by an ELISA kit affected by heterophilic antibodies.