Assessment of International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) Code Assignment Validity for Case Finding of Medication-related Hypoglycemia Acute Care Visits Among Medicare Beneficiaries

Objective: Administrative claims are commonly relied upon to identify hypoglycemia. We assessed validity of 14 International Classification of Diseases, Tenth Revision, Clinical Modification diagnosis code assignments to identify medication-related hypoglycemia leading to acute care encounters. Research Design and Methods: A multisite, retrospective medical record review study was conducted in a sample of Medicare beneficiaries prescribed outpatient diabetes medications and who received hospital care between January 1, 2016 and September 30, 2017. Diagnosis codes were validated with structured medical record review using prespecified criteria (clinical presentation, blood glucose values, and treatments for hypoglycemia). Sensitivity, specificity, and positive and negative predictive value (PPV, NPV) were calculated and adjusted using sampling weights to correct for partial verification bias. Results: Among 990 encounters (496 cases, 494 controls), hypoglycemia codes demonstrated moderate PPV (69.2%; 95% confidence interval: 65.0-73.0) and moderate sensitivity (83.9%; 95% confidence interval: 70.0-95.5). Codes performed better at identifying hypoglycemic events among emergency department/observation encounters compared with hospitalizations (PPV 92.9%, sensitivity 100.0% vs. PPV 53.7%, sensitivity 71.0%). Accuracy varied by diagnosis position, especially for hospitalizations, with PPV of 95.6% versus 46.5% with hypoglycemia in primary versus secondary positions. Use of adverse event/poisoning codes did not improve accuracy; reliance on these codes alone would have missed 97% of true hypoglycemic events. Conclusions: Accuracy of International Classification of Diseases, Tenth Revision codes in administrative claims to identify medication-related hypoglycemia varied substantially by encounter type and diagnosis position. Consideration should be given to the trade-off between PPV and sensitivity when selecting codes, encounter types, and diagnosis positions to identify hypoglycemia.