Performance analysis of automated evaluation of Crithidia luciliae-based indirect immunofluorescence tests in a routine setting - strengths and weaknesses.

BACKGROUND: Antibodies directed against dsDNA are a highly specific diagnostic marker for the presence of systemic lupus erythematosus and of particular importance in its diagnosis. To assess anti-dsDNA antibodies, the Crithidia luciliae-based indirect immunofluorescence test (CLIFT) is one of the assays considered to be the best choice. To overcome the drawback of subjective result interpretation that inheres indirect immunofluorescence assays in general, automated systems have been introduced into the market during the last years. Among these systems is the EUROPattern Suite, an advanced automated fluorescence microscope equipped with different software packages, capable of automated pattern interpretation and result suggestion for ANA, ANCA and CLIFT analysis. METHODS: We analyzed the performance of the EUROPattern Suite with its automated fluorescence interpretation for CLIFT in a routine setting, reflecting the everyday life of a diagnostic laboratory. Three hundred and twelve consecutive samples were collected, sent to the Central Diagnostic Laboratory of the Maastricht University Medical Centre with a request for anti-dsDNA analysis over a period of 7 months. RESULTS: Agreement between EUROPattern assay analysis and the visual read was 93.3%. Sensitivity and specificity were 94.1% and 93.2%, respectively. The EUROPattern Suite performed reliably and greatly supported result interpretation. CONCLUSIONS: Automated image acquisition is readily performed and automated image classification gives a reliable recommendation for assay evaluation to the operator. The EUROPattern Suite optimizes workflow and contributes to standardization between different operators or laboratories.

Neutrophil myeloperoxidase activity and the influence of two single-nucleotide promoter polymorphisms.

Myeloperoxidase (MPO) catalyses the formation of hypochlorous acid and is involved in many (patho)physiological processes. The present study was designed to determine the effect of two MPO promoter polymorphisms (463G/A and 129G/A) on enzyme activity. In 243 healthy controls, genotypes were determined and MPO activity was measured on a single-cell level using a haematological analyser. The 129G/A polymorphism reduces MPO activity in neutrophils, whereas for the 463G/A polymorphism, only gender-dependent differences in MPO activity in older age groups could be found. When studying these polymorphisms in disease, therefore, age and gender should be included in the analysis.