The present work evaluated the diagnostic accuracy of detection of Dengue NS1 antigen employing two NS1 assays, an
immunochromatographic assay and ELISA, in the diagnostic routine of Public Health laboratories. The results obtained with NS1
assay were compared with virus isolation and, in a subpopulation of cases, they were compared with the IgM-ELISA results obtained
with convalescent samples. A total of 2,321 sera samples were analyzed by one of two NS1 techniques from March to October 2009.
The samples were divided into five groups: groups I, II and III included samples tested by NS1 and virus isolation, and groups IV
and V included patients with a first sample tested by NS1 and a second sample tested by IgM-ELISA. Sensitivity, specificity, positive
and negative predictive values, Kappa Index and Kappa Concordance were calculated. The results showed that NS1 testing in groups
I, II and III had high sensitivity (98.0%, 99.5% and 99.3%), and predictive values and Kappa index between 0.9 - 1.0. Groups IV
and V only had Kappa Concordance calculated, since the samples were analyzed according to the presence of NS1 antigen or IgM
antibody. Concordance of 92.1% was observed when comparing the results of NS1-negative samples with IgM-ELISA. Based on the
findings, it is possible to suggest that the tests for NS1 detection may be important tools for monitoring the introduction and spread
of Dengue serotypes.
