Determination of first trimester specific reference interval of anti thyroid peroxidase antibody: a study from a tertiary care hospital of Pakistan

Objective: To determine the first trimester specific reference interval (RI) of Anti thyroid peroxidase antibody (TPO Ab) in pregnant subjects. Methodology: This study was conducted at Department Pathology, Aga Khan University Hospital, Karachi, Pakistan. 100 samples were used to determine the TPO Ab RI, collected from clinically euthyroid pregnant women within 12 weeks of pregnancy. Ninety five percent first trimesters specific gestational RI of TPO Ab was calculated by parametric and robust methods. Lower and upper reference limits were calculated at 2.5 and 97.5 percentile, respectively. Results: The reference intervals were found almost similar in both methods. The lower and upper reference values (IU/ml) were found 2.9, 24.6 and 2.8, 25.3 from parametric and robust methodologies, respectively. Conclusion: The reliable RI is vital to interpret the thyroid antibodies results of pregnant women for early screening and subsequent diagnosis and treatment. During pregnancy, an early diagnosis of autoimmune hypothyroidism may helpful to identify the pregnant women at risk of adverse pregnancy out comes.