Neonatal screening for congenital hypothyroidism in Estonia

Abstract

Screening for congenital hypothyroidism was carried out by measuring thyroid stimulating hormone (TSH) on dried blood spots (mean + 2SD cut oV value 12 µU/ml) by fluoroimmunoassay using DELFIA kits. A total of 20 021 infants were screened, and seven cases with congenital hypothyroidism were detected, giving an incidence of congenital hypothyroidism of 1:2860 (female:male ratio 6:1). In four of seven infants with congenital hypothyroidism (57%) the mother also had thyroid disease, supporting the importance of genetic factors as a cause of congenital hypothyroidism. Transient hyperthyrotropinaemia occurred in 654 infants (recall rate 3.3%). There was a significant association of transient hyperthyrotropinaemia only with cardiac failure at birth or caesarean section (p<0.01). Family studies showed no predisposition to thyroid diseases associated with a transient increase of TSH. (J Med Screen 1998;5:20-21) Keywords: neonatal screening; congenital hypothyroidism; thyroid stimulating hormone; hyperthyrotropinaemia Neonatal screening for congenital hypothyroidism, started in 1989, was the first genetic screening programme in Estonia.1 Methods Blood samples were obtained from 99% of newborns aged 3 to 5 days at three maternity hospitals and transferred to filter paper cards (Schleicher and Schuell No 2992). These cards contained information about the sex, nationality, birth date, date on which the sample was taken, gestational age, birth weight, height, and abnormalities of the infants. The cards were stored in bags between 2°C and 8°C for one to 14 days.Screening for congenital hypothyroidism was carried out by measuring the concentration of thyroid stimulating hormone (TSH) on a single dried blood spot specimen (punch size 3 mm with equivalent blood volume 4.8 µl by packed cell volume 50%) using a solid phase fluoroimmunoassay with the DELFIA neonatal hTSH kits (Wallac Oy, Turku). The fluorescence was read by the Arcus fluorometer 1230 (LKB, Wallac). The intra-assay and interassay variations were 4.5-6.6% and 4.7-5.7% respectively. The results from 415 normal newborns gave a cut oV value for TSH of 12 µU/ml (mean + 2SD).The screening was carried out in three stages: (a) TSH concentration was measured on the first dried blood spots in the institute laboratory; (b) when the TSH concentration was above the cut oV value the infants were recalled and TSH measurement repeated on a second filter paper; (c) if the TSH concentration when retested was still over the cut oV value TSH, thyroxine (T4), and triiodothyronine (T3) concentrations were measured in the serum to confirm the diagnosis. The diagnostic criteria for congenital hypothyroidism were: (a) a TSH concentration above the cut oV value (12 µU/ml) on the first and second blood spot analysis; (b) a TSH concentration in serum above normal (more than 15 µU/ml) but T4 and T3 concentrations below the normal value in serum; (c) the existence of clinical features of congenital hypothyroidism and an abnormal thyroid scan.When screening was positive, additional dat...

Cord Blood TSH Level Variations in Newborn – Experience from A Rural Centre in Southern India

“…Recently,another study from India by Gurjit Kaur et al, [9] from Chandigarh has taken 9µU/ml as the TSH cutoff value. Ruth V Mikelsaar et al, [10] from Estonia have taken the TSH cut -off value for neonatal screening as 12 µU/ml,which is a still lower cut-off value as compared to our study. The re-testing rate for our study i.e.…”

Rate of Recalls in Congenital Hypothyroidism Based upon a Regional Survey in Isfahan, Iran, Using Serum T4 and TSH Analyses: Comparison of Two Different Recall Methods

“…It was 0.16% in the Philippines, 0.35% in Austria, 0.3% in Greece, 0.28–0.29% in Hungary, 2.3% in Turkey and 3.3% in Estonia [15,16,17,18,19,20]. In a study in Thailand, the recall rate according to the cord TSH values greater than 30 mIU/l was 1.1% [21].…”

Screening for congenital hypothyroidism: results of screening 5600 Ardabil province infants

“…15,28 The rates of recall in other countries are usually different with the usual screening methods between 3-5 days after birth from 0.16% in the Philippines and 2.3% in Turkey to 3.3% in Estonia. 23,26,27 One of the reason for the high recall rate in this study is that due to the importance of illness and impose high economic cost, the TSH>5 was considered as the basis for recall that in other studies, the usual limit for screening of hypothyroidism is TSH>10 mu/L. 16 In this study, 56.7% of infants with permanent and transient hypothyroidism and 52.5% of infants with permanent hypothyroidism were girl.…”

“…In terms of low prevalence of hypothyroidism in Saudi Arabia female to male ratio 1.8 to 1, in Estonia 4 to 1 and in China 3 to 2, and in other studies in Mazandaran, as well as study by Siami and colleagues, this ratio was almost equal. 15,24,25,27 Among newborns with permanent and transient hyperthyroidism 39.1% and 32.5% of newborns with permanent hyperthyroidism had a positive history of disease. The relative familial relation in Ordoukhani study was 68.2%, which was higher than the present study and diet and environmental factors are involved in this, which requires more studies in the future.…”