Agreement between markers of population iodine status in classifying iodine status of populations: a systematic review

Abstract

ABSTRACT Background Population iodine deficiency is indicated by >3% of the population with newborn thyroid-stimulating hormone (TSH) concentration >5 mIU/L, median urinary iodine concentration (MUIC) <100 µg/L, or >5% prevalence of goiter in school-age children. However, the agreement between these population markers has not been systematically investigated. Objective To assess the agreement between TSH, MUIC, and goiter as markers of population iodine status. Methods We performed a systematic search for studies published on PubMed, Scopus, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Embase, and PsycINFO up to 29 October, 2018. Studies assessing iodine status in the population using the TSH marker and either MUIC or goiter prevalence in school-age children were included. The agreement between markers in classifying iodine status of the population was assessed. The sensitivity and specificity of the TSH marker was determined against MUIC and goiter prevalence as the reference markers. Results Of 17,435 records identified by the search strategy, 57 eligible studies were included in the review. The agreement between markers in classifying the iodine status of populations into the same category was 65% for TSH and MUIC, and 83% for TSH and goiter prevalence. The TSH marker had a sensitivity of 0.75 and specificity of 0.53 when compared with MUIC, and 0.86 and 0.50 when compared with goiter prevalence. Conclusions The TSH marker has a better agreement with goiter prevalence than MUIC when classifying the iodine status of populations. Re-evaluation of the current criteria for classifying the iodine status of populations using the TSH marker is warranted. This systematic review was registered at PROSPERO (http://www.crd.york.ac.uk/prospero/) as CRD42018091247.