Proficiency testing for urinary iodine and its impact on laboratory research related to iodine deficiency disorders (IDD) in the central Africa subregion

Abstract

The urinary iodine concentration (UIC) in humans is an essential component of the different phases of the fight against iodine deficiency disorders (IDD). As the etiology of goiter is diverse and the enlargement of the thyroid gland does not necessarily reflect the functional state or even the degree of iodine deficiency, the urinary iodine level reflects the true situation. Ambition for quality results pushed the iodine laboratory of the Centre for Food Safety and Nutrition Research, Yaounde, Cameroon, to participate in a proficiency testing (PT) programme initiated and coordinated by the Centre for Disease Control and Prevention (CDC) of the United States of America. Background This study investigated the impact of PT on research related to IDD in Central Africa. Materials and methods This study uses z scores and trends to evaluate the PT results of laboratories obtained with the CDC from 2001 to 2018. Values of z scores above 2.0 (or below − 2.0) were considered unusual values, whereas z scores above 3.0 (or below − 3.0) were outliers. Acceptable values of z scores were expected to fall between ± 2.0. Data were categorized into very low iodine (0–30 µg/l), low iodine (40–110 µg/l), medium iodine, (120–240 µg/l) and high iodine (250–600 µg/l) contents. Results The results of the acceptable z scores within ± 2.0 interval were 63.2%, 68.4%, 52.6% and 84.4% for very low, low, medium and high iodine contents, respectively. The overall trend indicates no significant difference between the iodine laboratory results and CDC target values (p > 0.05 in all cases). Conclusion Participation in the PT program enabled the laboratory to introduce a better standard operating procedure, improve sample treatment and reduce personal errors to the minimal level, achieving great progress in IDD research. Clinical trial number Not applicable.