Detection of dengue nonstructural 1 (NS1) protein in Vietnamese patients with fever

Diagnostic dengue in febrile patients is challenging. Of a total of 459 patients with acute undifferentiated fever, randomly selected from 12 primary health facilities and 1 clinic of the provincial malaria station in southern Vietnam, dengue-specific antibody (Ab) and NS1 Ag enzyme-linked immunosorbent assay (ELISA) (Platelia (TM) Bio-Rad Laboratories, Hercules, Ca 94547. US) were performed on acute (t3) and convalescent (t3 weeks) sera. Polymerase chain reaction (PCR) was used for confirmation. Based on a composite of the NS1 Ag-ELISA, Ab-ELISA, and PCR results. 54 (12%) patients had acute dengue. Positive and negative predictive values were 65% and 98% for the Ab-based diagnosis and 91% and 92% for NS1Ag, respectively. The agreement between Ab- and NS1Ag-based diagnosis was poor (k value, 0.2). Two patients without dengue had detectable NS1Ag on t0 and t3.1 just above the cutoff value and 1 with very high values. For 5 dengue patients, NS1Ag was still detectable at very high levels at t3. Dengue NS1Ag can be used for early diagnosis of dengue; infrequent false-positive results need further clarification. (C) 2009 Elsevier Inc. All rights reserved