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

Abstract

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 Sanità (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 and the first official round was carried out. Aim of the present paper is to compare 2015 and 2016 results and experiences. Methods: the scheme is prospective; participation is open to Italian laboratories performing sweat test analysis for CF diagnosis. Enrollment is voluntary and since 2015 the payment of a fee is required. Participants are registered and identified through a dedicated web-facility; each participant is identified by a specific Identification Number (ID) known only to the scheme organizer (ISS). Assessment covers analysis, interpretation and reporting of results. Results: thirteen and fifteen laboratories, belonging to the Italian public Referral Centers for CF, participated in the 2015 and 2016 round respectively. Seven laboratories participated constantly in the Italian EQA-SCT 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 (3 laboratories participated to both 2015 and 2016 schemes). Four laboratories made errors in chloride titration samples in 2015 but drastically improved their performance in 2016. In 2016 poor performance criteria were established and adopted: three laboratories (one participating in both 2015 and 2016 rounds and two first time participating) were marked as poor performers. 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.