Thyroid diseases are prevalent in Malaysia. A community health survey was undertaken to improve community awareness of the risks of common non-communicable diseases such as thyroid disorders and the benefits of screening for prevention and early detection of these conditions. Thyroid stimulating hormone (TSH) is the main biomarker and initial test for thyroid dysfunction. However, no formal reference interval (RI) data for TSH is available in Malaysia and South East Asia. All TSH reference intervals quoted in laboratory reports are from small verification studies laboratories conducted on 20 samples and thereafter adopting the manufacturer's data. We undertook to derive TSH RIs for Malaysia using the gold standard National Academy of Clinical Biochemistry (NACB) guidelines which state reference intervals should be established from healthy volunteers without personal/family history of thyroid dysfunction, no goiter/detectable thyroid autoantibodies and taking no medications.
Health screening was conducted during the 2016 Kembara Mahkota community event in Johor, Malaysia. Over one week, blood samples were taken from willing participants who attended the event after completing a brief health questionnaire. Samples were collected from 9.00 am to 2.00 pm daily and transported directly to the laboratory where they were processed within 4 hours. Samples were tested for a range of biomarkers (lipid, diabetes, cancer, and thyroid) on the Abbott Architect analyser at the Johor Specialist Hospital. Individuals identified as high risk were requested to seek further medical evaluation. Children, pregnant subjects, those with active medical conditions or on any medications were excluded. TSH and anti-thyroid peroxidase antibodies (anti-TPO) results were available from 2833 subjects. All samples with detectable TPO-Ab were excluded. Statistical analyses were performed using MedCalc software v 18.11.6 (Ostend, Belgium).
The distribution of TSH was slightly skewed to the right in the 2124 samples recruited, but log TSH was Gaussian in distribution.The parametric 95% reference interval for TSH in women is 0.47-3.08 and 0.47-2.84 in men. When compared to 5 other reported studies of Architect TSH RIs in the literature, our values for the lower reference limit lies in the middle of the range while the upper reference limit of TSH is amongst the lowest. Reference subjects were 18-80 years old (mean 40.3 ± 12.6). Mann-Whitney test for gender effects achieved statistical significance (p = 0.0388). When the group was divided by age bands in decades, the Kruskal-Wallis test for effects of age on TSH was not significant for both genders.
Community health projects such as ours are required to raise awareness of the risks of common preventable diseases, and to encourage individuals to participate in health checks and disease screening programmes. Besides, a study such as this has firmly established the TSH RIs for the Architect assay.