Comparision of the Recall Rate Using Two Different Diagnostic Criteria at Isfahan Screening Program for Congenital Hypothyroidism

Clinical diagnosis of congenital hypothyroidism (CH) is impossible without screening this disorder in neonates. Recall of neonates, on the other hand, is time consuming and results in economical and psychological burden on parents. The aim of this study was to evaluate the recall rate in congenital hypothyroidism screening project in Isfahan, using first an approach involving measures of both TSH and T4 and then using TSH alone, and comparing the results of each of the mentioned approaches with each other and other societies.

From June 2002 to August 2003, the blood of 3-7 day old neonates referred from 17 hospitals and maternity wards in Isfahan were collected the serum were separated and TSH and T4 level were measured. The level of TSH and T4 were measured using IRMA and RIA methods, respectively. If neonates’ serum TSH level was more than 20 mIU/L or T4 level was less than 6.5 m g/d, in the first step or TSH level was >20mIU/L in the second step, they were recalled. Neonates with TSH>10 and T4<6.5 on their next measurement after the recall, were considered as congenitally hypothyroid ones, and underwent treatment.

Serum T4 & TSH of 39601 neonates were measured in this study (29493 and 10108 neonates by first and second recall approach, respectively). Seven hundred neonates were recalled (647 neonates on the first step and reminder based on the second step). Recall rate on the first stage was higher than the second stage (2.2% VS 0.5%, p<0.05). Most of the recalled neonates in the first recall step were recalled for low T4 level (p<0.05). The prevalence of CH was one in 338 live births.

Although recall rate was in acceptable range both by first and second step, but using TSH alone for screening and recalling seems to be more practical and effective in our society, than using both T4 and TSH for this purpose.