Newborn screening for congenital hypothyroidism through dried blood spot in Low middle income country (LMIC): Experience from a tertiary care center

Background: Neonatal screening is a preventive strategy for various endocrine,metabolic and genetic conditions.Congenital hypothyroidism (CH) is one of the most common preventable and treatable causes of intellectual disability,and delayed diagnosis can lead to disastrous consequences.Incidence of CH is1:3000-1:4000 neonates worldwide but data varies globally.Pakistan lacks a national newborn screening programme for any inherited disease,but Aga Khan University Hospital (AKUH) is doing newborn screening for Congenital Hypothyroidism (CH).Since April 2019 CH screening is done through dried blood spot (DBS). Pakistan has a very scarce data regarding incidence of CH,indicating the importance of working in this direction.We present our data on CH screening through DBS over a period of two and a half year.Objective: To determine the proportion of screen positive newborns(\u3e33 weeks gestation) between April 2019 –October 2021,for Congenital Hypothyroidism as part of newborn screening programme done through DBS and also to identify confirmed CH cases on serum TSH testing.Methods: Retrospective review of Laboratory data of DBS TSH levels of neonates \u3e33 weeks of gestation from April 2019-October 2021.Screening is done between 48-72 hours of life and after 24 hours in case of early discharge.TSH is quantitatively determined and values ≥10 μIU/ml were taken screen positive,up to10 μIU/mL were taken normal,between 10-20μIU/mL were considered ambiguous, above 20 μIU/mL were labeled as presumptive positive. Ambiguous and presumptive positive babies were recalled to get TSH+/-FreeT4 tests.CH was confirmed on the basis of low FT4 and highTSH \u3e10μIU/ml and treatment was started.Results: 97%(14283 out of 14379)of the live born babies were screened for Congenital Hypothyroidism. To identify safe minimum recall criteria, babies were recalled if the DBS TSH level was more than 10 mU/l and if they were not preterm(\u3c33 weeks).226 (96%) out of 235 screen positive babies were recalled,out of which serum TSH and/or FT4 was repeated in 158 babies(70%). Recall rate being 96%.15 newborns were diagnosed Congenital hypothyroidism through serum TSH testing and started on treatment within 2 weeks of life. Proportion of babies diagnosed with Congenital Hypothyroidism is 0.10% with average incidence rate being 1:1000 babies.\u3e \u3e33 weeks).226 (96%) out of 235 screen positive babies were recalled, out of which serum TSH and/or FT4 was repeated in 158 babies(70%). Recall rate being 96%.15 newborns were diagnosed Congenital hypothyroidism through serum TSH testing and started on treatment within 2 weeks of life. Proportion of babies diagnosed with Congenital Hypothyroidism is 0.10% with average incidence rate being 1:1000 babies.Conclusion: Due to high incidence rate of CH in our neonates, implementating a national screening program and also conducting further studies to determine the main risk factors for the high incidence of CH is essential. Overall coverage of CH screening programme at AKUH has been 97% which need to be further increased