Glycosylated hemoglobin as a screening test for hyperglycemia in antipsychotic-treated patients: a follow-up study

PURPOSE: To assess the point prevalence of undetected prediabetes (preDM) and diabetes mellitus (DM) in patients treated with antipsychotics and to compare metabolic parameters between patients with normoglycemia (NG), preDM, and DM. Furthermore, conversion rates for preDM and DM were determined in a 1-year follow-up. PATIENTS AND METHODS: In a naturalistic cohort of 169 patients, fasting glucose (FG) and hemoglobin A(1c) (HbA(1c)) criteria were applied at baseline and at follow-up after 1 year. A distinction was made between baseline patients diagnosed according to FG (B-FG) and those diagnosed according to HbA(1c) (B-HbA(1c)). Conversion rates in the 1-year follow-up were compared between B-FG and B-HbA(1c). RESULTS: At baseline, preDM and DM were present in 39% and 8%, respectively. As compared to patients with NG, metabolic syndrome was significantly more prevalent in patients with preDM (62% vs 31%). Although the majority of patients were identified by the FG criterion, HbA(1c) contributed significantly, especially to the number of patients diagnosed with preDM (32%). Regarding the patients with preDM, conversion rates to NG were much higher in the B-FG group than in the B-HbA(1c) group (72% vs 18%). In patients diagnosed with DM, conversion rates were found for B-FG only. CONCLUSION: PreDM and DM are highly prevalent in psychiatric patients treated with antipsychotic drugs. HbA(1c) was shown to be a more stable parameter in identifying psychiatric patients with (an increased risk for) DM, and it should therefore be included in future screening instruments.