Incidence of congenital hypothyroidism in Western Rajasthan using cord blood thyroid-stimulating hormone levels as a screening tool: A cross-sectional hospital-based study

Background: Congenital hypothyroidism (CH) is considered the most common preventable cause of intellectual impairment, with a worldwide annual incidence of 1:4000 live births. In the absence of screening program actual incidence in India is not exactly known, but in previous studies it varies from 1:500 to 1:3400. We wished to find out the incidence of CH in Western Rajasthan using cord blood TSH as a screening tool and venous TSH within 14 days of life as a confirmatory test. Methods: This cross sectional descriptive study was conducted over a period of six months in teaching hospitals attached to Medical College. Cord blood TSH value of 20 mIU/L or >20 mIU/L was taken as cut off for screening and all screen positive neonates were re-tested for serum TSH by taking venous samples within 14 days of life. Repeat TSH levels of 20mIU/L or more tested by Enzyme Linked Fluorescent Assay were considered confirmatory. Results: Total 9558 cord blood samples were analyzed for TSH levels, out of which 533 came out to be screen positive (recall rate 5.57%). Out of these 58 could not be confirmed, so were excluded from the further analysis. Effective sample size and screen positive cases dropped to 9500 and 475 respectively, and out of these 13 were confirmed as CH (incidence - 1.37 per thousand live births). Conclusions: Considering the previous studies, incidence of CH is much higher in Western Rajasthan than the anticipated. Overall in India CH seems to be more prevalent than the other parts of the world, necessitating the need of national screening program