A comparative, prospective study of serological, virus isolation and PCR amplification techniques for the laboratory diagnosis of dengue infection

Serum specimens from 58 hospitalized patients with clinical suspicion of dengue fever were obtained in a prospective study. All 58 acute serum samples were tested by IgM capture enzyme-linked immunosorbent assay (ELISA) and commercial Dengue Blot serological assays, virus isolation in C6/36 mosquito cells, and polymerase chain reaction (PCR) by single-step and semi-nested approaches using NS3 gene primers. Of the 22 acute sera positive by any one of the five methods, 17 (77.3%) were positive by IgM capture ELISA, 12 (54.5%) by Dengue Blot, none (0%) by virus isolation, two (9.1%) by single-step PCR and three (13.6%) by the more sensitive semi-nested PCR approach. Dengue virus type 2 was detected by both PCR assays. Convalescent sera were also collected from 13 of the 58 patients and haemagglutination inhibition (HI) tests performed on paired serum samples. HI confirmed five positive sera, while the other eight sera were negative or inconclusive. In our study cohort, although PCR was more sensitive than virus isolation for detecting the presence of dengue virus in sera, serological techniques were able to identify more dengue infections than both PCR and virus isolation. These results may be attributed to the collection of serum samples after the period of viraemia which is appropriate for serological assays, in contrast to early or highly viraemic sera which are more suitable for PCR and virus isolation methods.