Interpreting insulin immunoassays during investigation of apparent spontaneous hypoglycaemia and insulin overdose.

We report two cases of hypoglycaemia; one with apparently spontaneous hypoglycaemia and one with presumed insulin overdose. In both cases insulin concentration was normal when measured with the Roche immunoassay, but elevated when remeasured with the Advia Centaur immunoassay and a diagnosis of hypoglycaemia secondary to insulin analogue administration was made. These cases highlight that physicians need to understand the binding characteristics of the insulin immunoassay they use.