Improving dengue case confirmation by combining rapid diagnostic test, clinical, and laboratory variables

BackgroundDengue is the most widely distributed arboviral disease in tropical and subtropical countries. Early diagnosis is difficult, and most of the suspected cases are diagnosed according to clinical criteria. In underdeveloped countries, laboratory tests are done on a proportion of dengue with warning signs or severe dengue suspect cases. This study aimed to design a diagnostic algorithm using rapid diagnostic tests (RDT), ELISA tests together with clinical and hematology variables to confirm dengue cases in febrile patients from an endemic area in Colombia. Methods and resultsA total of 505 samples were collected from patients with acute febrile syndrome (<7 days) assisted to the Municipal Hospital in Girardot (Colombia). Serum samples were evaluated by rapid diagnostic tests -RDT- (IgM and IgG antibodies and NS1 antigen immunochromatographic assay), capture ELISAs (IgM, IgG, and NS1 antigen), and by RT-PCR. We analyzed individual tests performance to determine which were the most useful to confirm dengue cases. Individual results for IgM, IgG, and NS1 RDT yield low sensitivity and specificity values than the reference standard. A high sensitivity (96.3%) and specificity (96.4%) were obtained after combining the IgM and NS1 ELISAs results. The analysis using the combined NS1 RDT and IgM ELISA results showed 90.3% sensitivity and 96.2% specificity. Adjusted odd ratios (aOR) were calculated including data from symptoms, signs, and diagnostic laboratory tests to differentiate dengue from other febrile illnesses (OFI). Myalgia (aOR: 1.87, CI95%: 1.04-3.38), abdominal tenderness (aOR: 1.89, CI95%: 1.14-3.10), platelets count <140.000/mm3 (aOR: 2.19 CI95%: 1.31-3.67). The analysis using the results of the diagnostic test yields significant ratios for IgM RDT (aOR:2.63 CI95%: 1.59-4.33) and NS1 RDT also differentiate dengue cases from OFI. Combined positive IgM or NS1 RDT and the one that combined positive NS1 RDT or IgM ELISA detect dengue cases in 81.6% and 90.6%, respectively (p<0.001). ConclusionOur findings showed that only clinical diagnosis does not confirm true dengue cases dengue and needs to be complemented by laboratory diagnostic tests to stablish the diagnosis. We also demonstrate the usefulness of rapid tests in diagnosis, suggesting their implementation with IgM ELISA test to better confirm dengue cases. Author SummaryDengue infections are considered the main mosquito-borne viral disease and a considerable concern in public health in tropical countries. Transmission has been associated with population growth, globalization (rapid urbanization, increasing movement of people), and environmental changes. Dengue diagnosis is difficult because of clinical variability in population of different age groups, with different degrees of severity that can have a fatal outcome. Diagnosis must consider clinical and laboratory criteria to improve early case confirmation particularly in endemic areas, where there is a need to support health services and improve treatment and management of the disease.