Importance of screening with oral glucose tolerance test for early diagnosis of cystic fibrosis-related diabetes mellitus

Abstract

To evaluate (a) the prevalence of cystic fibrosis-related diabetes mellitus (CFRD) in a non-Caucasian population treated in a University Hospital in São Paulo, Brazil; and (b) if annual screening of patients with cystic fibrosis (CF) ≥ 10 yr of age, with oral glucose tolerance test (OGTT), resulted in early detection of CFRD. A cross-sectional study was performed with retrospective/prospective analysis of CF patients ≥10 yr of age. Various parameters were analyzed. Patients previously diagnosed with CFRD had their parameters collected at the time of diabetes diagnosis; others were submitted to annual OGTTs, with the parameters collected at the time of their last OGTT. A total of 60 subjects [29 females/31 males; mean age 19.1 yr (±7.6)] were analyzed. In our group of CF patients, we found that 30% had CFRD, 26.7% had altered response to OGTT, and 43.3% had normal glucose tolerance. Analysis of those patients with CFRD showed that the mean age at the time of diagnosis of CFRD, in patients diagnosed by OGTT screening, was 13.5 yr (±2.9) vs. 22.3 yr (±5.4) among those previously diagnosed by clinical suspicion (p < 0.001). The prevalence of CFRD in our patients is high, similar to the data from Caucasian populations, and significantly higher than previously reported in Brazil. Screening with OGTT resulted in earlier diagnosis of CFRD by 8 yr. These data may help convince national CF centers that CFRD is frequent, and that screening should be mandatory.