Quality control assessment for the serological diagnosis of dengue virus infections.

BACKGROUND A major drawback of modern society's rapidly increasing mobility is the ease with which dangerous infections can be imported into Europe. Often these infections are not diagnosed because physicians are not familiar with the symptoms and laboratory tests are not always available in local diagnostic centres. Improving diagnostics is the most important step in detecting and dealing with these pathogens and quality control measures are, therefore, essential tools. OBJECTIVES To assess the diagnosis of imported dengue virus infections in Europe by (1) running a pre-evaluation panel (four serum samples, sent out in 1999) and optimising sample preparation and shipping procedures and (2) initiating an External Quality Assurance (EQA) program (20 serum samples, sent out in 2002). STUDY DESIGN All serum samples sent out were to be tested for the presence of dengue virus-specific IgM and IgG. For the pre-evaluation panel, four samples were distributed (one sample IgM+/IgG+, one sample IgM-/IgG+, two samples IgM-/IgG-) and for the EQA 20 samples (12 samples IgM+/IgG+, five samples IgM-/lgG+, one sample lgM+/IgG- two samples IgM-/IgG-). 13 laboratories took part in the pre-evaluation panel and 18 laboratories participated in the first EQA run. RESULTS For the pre-evaluation panel, the participants reported concurrent and correct results for 88% of the IgG-positive samples and for 100% of the IgG-negative samples. The results for the IgM-positive sample were correct in 91% of the reported tests and in 97% of the IgM-negative samples. For the EQA, the participants reported concurrent and correct results for 71% of the IgG-positive samples and 89% of the IgG-negative samples. 58% concurrent and correct results were reported for the IgM-positive samples and 97% for the IgM-negative samples. CONCLUSIONS The results presented here demonstrate the importance of quality measures for imported viral pathogens like dengue viruses and clearly indicate the need for improving the existing test systems.