Italian external quality assessment program for cystic fibrosis sweat chloride test: a 2015 and 2016 results comparison

Background. Diagnostic testing in cystic fibrosis (CF) is based on the sweat chloride test (SCT) in the context of appropriate signs and symptoms of disease and results of the gene mutation analysis. In 2014 the Istituto Superiore di Sanita (ISS) established a pilot Italian external quality assessment program for CF sweat chloride test (Italian EQA-SCT). In 2015 this activity was recognized as a third party service carried out by the ISS. The aim of the paper is to compare 2015 and 2016 results and experiences. Methods. The scheme is prospective; enrollment is voluntary and the payment of a fee is required. Participants are registered and identified by a specific Identification Number (ID) through a dedicated web-facility. Assessment covers analysis, interpretation and reporting of results. Results. Thirteen and fifteen laboratories, participated in the 2015 and 2016 round respectively. Seven laboratories participated constantly from 2014, eleven participated both in 2015 and 2016 and four participated in 2016 for the first time. Variability in scores of chloride titration and heterogeneity in interpretation/reporting results were detected in both rounds. A total of 18 critical errors in chloride titration were made by eight different participants. Four laboratories made errors in chloride titration in 2015 but drastically improved their performance in 2016. In 2016 poor performance criteria were established and adopted. Conclusions. Even though results show variability in performance of laboratories, constant and mandatory participation may contribute to the improvement of performance and quality reached by laboratory.