Evaluating performance in sweat testing in medical biochemistry laboratories in Croatia

Sweat test has a diagnostic role in evaluation of cystic fibrosis. Its performance includes sweat stimulation, collection and analysis. All listed may be sources of inconsistencies in everyday practice. The aim of this study was an evaluation of external quality assessment (EQA) of sweat chloride measurement including sweat test performance in medical biochemistry laboratories in Croatia.

EQA for sweat chloride measurement was provided by Croatian Centre for Quality Assessment in Laboratory Medicine (CROQALM) in five consecutive exercises to medical biochemistry laboratories (MBL) that offered sweat testing. A questionnaire regarding all phases of testing was mailed to involved MBL (N = 10). Survey results were compared to current guidelines for sweat test performance.

Reported results of EQA in 2015 exercises showed coefficients of variation (CV) from 28.9%, 29.0% to 35.3%, respectively. An introduction of uniform sweat chloride measurement protocol resulted in CV of 15.5% and 14.7% reported in following two exercises in 2016. All MBL included in this study replied to the questionnaire. Results reported by MBL indicated: lack of patient information policy (7/10), use of unacceptable electrodes (6/9), misuse of minimum of acceptable sweat weight (6/9), lack of internal quality assessment (5/9) and recommended reference ranges (5/9 and 4/9). Agreements to guidelines were found in approach to unsuitable patients (9/10) and sweat collection (8/9).

Presented results indicate major weak points of current practice in sweat test performance in Croatian MBL and stress the need for its standardization on a national level.