Case Report: A 66-year-old woman repeatedly presented with symptomatic
hypoglycemia. At the first presentation, the serum
glucose level was 40 mg/dL (2.2 mmol/L),
C-peptide level was 13.1 ng/mL (0.8-3.1 ng/mL),
proinsulin level was 96.9 pmol/L (<18.8 pmol/L), and
insulin level was 164 mU/L (<17 mU/L). An initial
hypoglycemic agent screening, performed 24 hours after admission, yielded a negative result, leading to prolonged and recurrent hospitalizations for workup and localization of
insulinoma. A
hypoglycemic agent screening at a subsequent presentation, concordant with
hypoglycemia, yielded a positive result for
glipizide, which was at a level of 320 ng/mL (reporting limit, 40 ng/mL). An examination of the patient's home medications revealed a container, labeled as
benztropine, containing
glipizide tablets. After the diagnosis of
glipizide-induced
hypoglycemia, the patient had no further episodes of
hypoglycemia.
Discussion: The failure to detect
glipizide using the initial
hypoglycemia agent assay was likely because of a combination of a delay in the initial screening and low sensitivity of the assay for
glipizide compared with that of other available assays. Here, we discuss important considerations for the interpretation of
hypoglycemic agent screening in the diagnosis of
hypoglycemia, including the timing of collection and reporting, pharmacokinetics of culprit agents, and sensitivity of the
hypoglycemic agent panel used.
Conclusion: