Distribution of TSH levels in dried blood spot among 137,207 Greek newborns: incidence of Primary Congenital Hypothyroidism and Transient Hyperthyrotropinemia

Abstract

In September 1979 screening for Congenital Hypothyroidism (C.H.) was started in Greece. As the screening method Thyroid-Stimulating Hormone (TSH) determination in dried blood spots collected on the 5th day of life was chosen. To date 137,207 newborns (65% of all live births in Greece) have been screened. The distribution of TSH levels in a single estimation was as follows: < 12.5μIU/ml 87.7%, 12.5-30μIU/ml 11.4% and > 30μIU/ml 0.9%.Values > 30μIU/ml were confirmed by a second estimation from the initial card in 171 cases, which were recalled for a new blood specimen (recall rate 0.12%). Among them 97 had TSH values between 30 and 50μIU/ml and TSH estimation from a blood spot on a new card 1-3 months later showed TSH values < 12.5μIU/ml. In 41 cases with TSH values 50-80μIU/ml, serum TSH and T4 revealed 4 cases of C.H. (9.7%), while 37 cases had serum TSH and T4 values within normal limits and were considered as Transient Hyperthyrotropinemias (T.H.). Finally among 33 cases with initial TSH values > 80μIU/ml, in 29 (88%) the diagnosis of C.H. was confirmed on biochemical and clinical grounds, while 4 were considered as T.H. The overall incidence of primary C.H. in our population was 1:4,157.