Diagnostic biologique de la dengue.

Dengue is the most important disease caused by an arbovirus worldwide. Its clinical manifestations are very large from asymptomatic infections to severe diseases with fatal outcome. No effective antiviral treatment or vaccine is available. Thus, a rapid and accurate diagnosis is of paramount importance both for better clinical case management and surveillance. Diagnosis methods depend on the time clinical signs appeared. Within the 7 first days of fever, direct tests are preferred. RT-PCR methods are sensitive, specific, and can identify viral serotypes. Conventional RT-PCR will probably be replaced by real time PCR as soon as standardised and accurate assays for the four serotypes will be available. Serology (EIA) is used only after 7 days of disease, i.e. late in the course of dengue; it is accurate, specific but not discriminatory for serotypes and high cross-reactive. NS1 antigen detection still lack of clinical sensitivity and viral isolation is too fastidious. Even though ameliorations are necessary, viral detection by RT-PCR remains the best tool in clinical settings for a rapid diagnosis of severe dengue infections.

Prospective evaluation of nonstructural 1 enzyme-linked immunosorbent assay and rapid immunochromatographic tests to detect dengue virus in patients with acute febrile illness.

We prospectively evaluated the Bio-Rad nonstructural 1 (NS1) enzyme-linked immunosorbent assay (ELISA) and lateral flow immunochromatographic assay (LFIA) in comparison to an in-place reverse transcription-polymerase chain reaction for dengue diagnosis. Among 537 consecutive samples from patients with acute febrile disease, 264 (49.2%) tested positive in reverse transcription-polymerase chain reaction (RT-PCR), 156 (29.1%) in NS1-antigen (Ag) ELISA, and 125 (23.3%) in NS1-Ag LFIA. Compared to the RT-PCR status, the specificity was 100% for the NS1-Ag ELISA and LFIA, but their respective sensitivities were 61.2% [95% confidence interval (CI), 55.2-67.2] and 49.4% (95% CI, 43.2-55.6), with nadirs of 37.9% and 24.1% on day 6 of illness. The NS1-Ag ELISA and LFIA were positive, respectively, for 48.0% and 40.7% of the secondary infections versus 85.0% and 66.7% of the primary infections. For patients <5 years old, NS1-Ag ELISA and LFIA reached respective sensitivities of 100% and 90.5%. Reports of results of dengue NS1-Ag assays should specify that negativity does not preclude DENV infection, and require further investigations in the case of severe disease.