Non-structural protein 1 (NS1) of dengue virus detection correlates with severity in primary but not in secondary dengue infection

Background: Non-structural protein 1 (NS1) of dengue virus circulates in the serum of patients during the acute phase of the disease. Objectives: To determine whether NS1 screening can serve in diagnosing primary and secondary infection and to evaluate its utility as a marker for predicting the severity of dengue in children. Study design: Patients <= 15 years of age hospitalized for dengue between 2012-2018, with NS1 determination (Panbio, Australia) were included. Clinical y laboratorial characteristics were collected in a standardized data table for analysis of correlation between serotypes, primary or secondary condition of infection, severity, and presence of NS1. Results: Of 709 children hospitalized for dengue with NS1 determination, 479 (67.5 %) had the positive test. Of the 378 primary cases, 320 (85 %) were NS1 (+). while among the 242 secondary cases only 103 (42.5 %) were NS1 (+) (p < 0001). Of the 479 patients with NS1 (+), 344 (72 %) were warnig-signed cases (WSC) and 94 (19 %) were severe cases (SC), being these figures 62 % and 34 %, in the NS1 negative patients respectively (p < 0.001). There was no difference in the frequency of WSC or SC between patients with NS1 positive or negative test in secondary dengue; however, in primary dengue, the figures were 68 % vs 32 % (p < 0.001), and 87 % vs 12 % (p < 0.001), respectively. Conclusions: The presence of NS1 positive test is associated with the condition of infection (primary or secondary) and exhibited an increased risk of developing forms with warning signs or severe dengue in primary cases, but not in secondary cases.