Retrospective Evaluation of Oral Glucose Tolerance Test in Young Patients with Transfusion-Dependent Beta-Thalassemia

Current guidelines recommend yearly evaluation of glucose metabolism with oral glucose tolerance test (OGTT) in patients with thalassemia major (TM) from their 10th year onwards.

The aim of the study was to retrospectively evaluate all the OGTT tests performed in a single pediatric center during the last decade and assess the necessity of yearly performed OGTT in patients with TM during the second decade of life.

One hundred and seventy tests performed on 39 patients (24 boys) were included in the analysis. Mean age at the time of each OGTT was 14.15 ± 2.79 years. Seventeen tests (10%) in 8 patients (5 boys) were characterized as impaired glucose tolerance (IGT), whereas in 2 tests (1.18%), fasting glucose values were above 200 mg/dL (diabetes mellitus). Acknowledging the fact that there could be sporadic technical errors, especially in fasting glucose abnormal values, we selectively separated patients with either IGT and abnormal HOMA, MATSUDA, or QUICKI indices or persistently impaired fasting glucose or IGT. With these criteria, 7 patients (4 boys) were identified. No significant differences were observed in demographic and anthropometric parameters, ferritin levels, and mean volume of blood transfused in patients with a definite abnormal glucose metabolism. In order to address selection criteria for performing OGTT without missing a single patient with a definite glucose intolerance, these criteria should include (i) a first OGTT test at the initiation of puberty, (ii) OGTT in any patient with a fasting glucose above 100 mg/dL, and (iii) OGTT in any patient with a ΗΟΜΑ-IR index above 1.85 and yearly onwards. By adopting these criteria, total OGTT tests performed could have been reduced from 170 to only 91, translating to a significant reduction of 46.47%.

Only a small percentage of young patients with transfusion-dependent b-thalassemia exhibit abnormal glucose metabolism during their second decade of life. By adopting specific selection criteria, one may avoid performing this time- and money-consuming test in a significant proportion of patients, albeit without sacrificing timely detection and intervention.