ESPE Abstracts

Background: In children, untreated Congenital Hypothyroidism (CH), can result in permanent neurological defects and growth abnormalities. This can be prevented by early detection and treatment of CH. Newborn screening for CH is considered one of the best tools for the prevention of these long-term complications. In our setting, we use heel-stick dried blood sample TSH (DBS-TSH) as a screening tool to detect CH. The DBS-TSH cut-off level is critical to ensuring that true cases of CH are not missed. The purpose of this study is to evaluate the positive predictive value of DBS-TSH levels in diagnosing CH.

Objective: To evaluate the positive predictive value of DBS-TSH in diagnosing congenital hypothyroidism in neonates born at a tertiary care hospital.

Design: Descriptive Cross Sectional Study

Setting: Aga Khan University Hospital, Neonatal screening program

Sample Size: The study included all neonates (33 weeks or above gestation age) who were delivered during the period from April 2019 to December 2022 and screened for DBS-TSH as a part of routine newborn screening.

Method: All neonates with a value of DBS-TSH more than 10mlU/L were considered as screen positives. All screen positives were contacted by Newborn screening team (NBS Team) and advised to get Confirmatory Serum TSH done. Short-term follow-up was done for all screen positive cases within one week of issuance of initial DBS-TSH results, and continue to follow them for two weeks, and Information about Confirmatory testing, date and results was recorded. Neonates with plasma TSH >20Miu/L were considered as true positives and paediatric endocrinology team followed these patients to start treatment. A follow-up was considered ‘Lost to Follow’ if due to any reason not able to contact patient or confirmatory test not done after two weeks of initial screen positive.

Results: Newborn screening for CH (DBS-TSH) was performed in 30402 neonates out of which 542 (1.78%) were screen positives. 172 (31.73%) patients were lost to follow and in 379 (69.92%) patients confirmatory Serum TSH was done in which 27 were true positives and diagnosed as CH. The Positive predictive value of DBS-TSH was 0.0712 or 7.12%.

Conclusion: Among those neonates who had a positive screening test, the probability of the disease is 7.12%. We plan to further sub divide screen positives into groups based on initial results (10-20, 20-30 and >30) and calculate the PPVs in order to adjust the cut off values to increase the yield of DBS-TSH.