Diagnostic comparison between cord blood and filter paper for the screening of congenital hypothyroidism

Background: Cord-blood and heel-prick TSH levels are essential in diagnosing and preventing the serious complications of congenital hypothyroidism, which mainly include intellectual disability. The study aimed to compare between cord-blood and heel-prick TSH sensitivity and specificity in detecting congenital hypothyroidism (CH) among newborn screened babies.

Method: The study included 21,012 newborn screened babies for congenital hypothyroidism starting from September 2013 until March 2019. Both cord-blood and heel-prick TSH were collected from each newborn. Heel prick and cord-blood TSH cutoff values of >21 μU/ml and >30 mIU/L respectively were considered positive.

Results: Out of the total screened newborns, 12 were confirmed for having primary congenital hypothyroidism. Nine cases were positive for cord-blood TSH (Sensitivity 75%, specificity 99.9%, and a recall rate of 0.004%), while 139 cases were positive for heel-prick blood TSH (Sensitivity of 100%, specificity of 99.3%, and a recall rate of 0.60%).

Conclusion: For the screening of CH, heel prick is considered a superior method, but cord blood remains a practical option due to its cost-effectiveness, immediate action, and lower recall rate. Therefore, whenever recall is difficult and/or early discharge is the practice, cord blood is an alternative method to heel prick but not with cases of prematurity.