Hoffmann's Indirect Method-Based Establishment of Reference Interval of Thyroid Stimulating Hormone In Neonates: An Initiative Towards Less Biased Thyroid Status Screening in Neonates of Chamarajanagar

Background:  Congenital hypothyroidism (CH) is among the leading preventable cause of intellectual disability in neonates. Measurement of thyroid stimulating hormone (TSH), remains as a most reliable biochemical test to diagnose CH. The Clinical Laboratory Standards Institute recommends using local population and age-specific TSH reference range for assessing the thyroid status. Hoffmann’s indirect computerized method is adopted by laboratories for estimation of RI, as it closely approximates the true RI. The study aimed to establish the RI of TSH in neonates using Hoffmann's indirect method.

Materials &Methods: The TSH data of new-born aged 0-30 days tested between 2022 to 2024 at the Maternal and Child Health Hospital of CIMS, Chamarajanagar were retrospectively retrieved from archives of Clinical Biochemistry laboratory. First report of TSH was obtained. Data were analyzed using Hoffmann’s indirect method to derive age-specific RIs for the local population, based on Chemiluminescence Immunoassay technique.

Results: The TSH RI determined by Hoffmann’s indirect method was 0.23–5.52 μIU/mL for neonates aged 0–7 days and 0.38–8.92 μIU/mL for those aged 8–30 days. These intervals differed notably from the manufacturer’s reference range (0.3–4.2 μIU/mL), underscoring the need for population-specific calibration.

Conclusion: Laboratory-specific reference intervals are crucial for accurate interpretation of biochemical test results. Hoffmann’s indirect method provides a simple and effective approach for deriving such customized RIs. The newly established TSH RIs are specific to the local population, assay method, and neonatal age group, and will henceforth be employed for evaluating thyroid status in neonates at this institute.