Diagnostic parameters and reliability of four rapid immunochromatographic tests for dengue 4

ABSTRACT Background: Although performance of rapid immunochromatographic tests (RITs) for dengue virus (DENV) serotypes 1, 2 and 3 is relatively settled, evidence on accuracy of RITs for DENV-4 are based on studies with small sample sizes and with discrepant results. Objectives: To assess accuracy and inter-observer agreement of RITs targeting dengue nonstructural protein-1 (NS1) antigen - Dengue NS1-Bioeasy™, Dengue NS1 Ag Strip-Bio-Rad™, IVB Dengue Ag NS1-Orangelife™ and Dengue NS1-K130-Bioclin™ in DENV-4 samples. Methods: Study sample (n = 324) included adults presenting at an emergency unit in Rio de Janeiro, Brazil, with fever of ≤72 h and two or more dengue symptoms. A serum sample from each patient was tested by each RIT. A positive reverse-transcription polymerase chain reaction was considered as the reference standard for dengue diagnosis. The diagnostic parameters analyzed for each RIT were sensitivity, specificity, positive and negative predictive values, and likelihood ratios. Each RIT was read by homogeneous (two junior nurses) or heterogeneous (one junior nurse and one senior biologist) pairs. Agreement was estimated by simple kappa with 95% confidence interval, positive (Ppos) and negative (Pneg) proportion concordance and prevalence and bias adjusted kappa, rated from poor (k < 0.0) to almost perfect (0.8 < k < 1.0), and perfect (k = 1). Results: NS1 RITs for DENV-4 diagnosis showed high specificity (95.9%-99.4%), but low sensitivity (14.7%-45.4%). Bioeasy™ had the best performance, with a positive likelihood ratio of 26.0 (95% CI: 8.4;81.0). Inter-observer agreement was almost perfect for all evaluated RITs. Mismatches in confirmed dengue were more common for the Bioclin™ (Ppos 88.3-90.0 %) and Orangelife™ (Ppos 91.7-94.1 %) tests. Conclusions: For DENV-4, the tested RITs had high specificity, but lower sensitivity compared to published results for other serotypes. They should not be used for screening purposes. Different brands may have very different performances. This should be considered upon deciding of using RITs in DENV-4 outbreaks.

Antígeno NS1 dos Vírus Dengue: desempenho de testes disponíveis comercialmente e aplicações alternativas para o diagnóstico precoce das infecções por dengue / Dengue virus NS1 antigen of: commercially available test performance and alternative applications for early diagnosis of dengue infections

O objetivo deste trabalho foi avaliar o desempenho e as aplicações alternativas dos testes de captura de NS1 disponíveis comercialmente. O desempenho dos testes Platelia NS1 ELISA (BioRad Laboratories) e pan-E Early ELISA, primeira geração (PanBio Diagnostics) e do teste rápido Ag Strip (BioRad Laboratories) disponíveis no mercado após a introdução destes no país, foi avaliado com um painel de 450 amostras. Dentre os três kits analisados, o teste NS1 Ag Strip foi o mais sensível (89 porcento, 197/220), seguido pelo Platelia NS1 ELISA (84 porcento, 184/220). O menos sensível foi pan-E Early ELISA com 72 porcento (159/220) de sensibilidade. Uma menor sensibilidade foi observada em casos de DENV-3 por todos os três kits analisados. A comparação de duas gerações do ELISA para a captura de NS1 do fabricante PanBio Diagnostics (pan-E Dengue Early ELISA e Early ELISA Dengue, segunda geração), após o aperfeiçoamento do teste pelo fabricante, demonstrou um aumento significativo na sensibilidade, de 72,3 porcento (159/220) para 80 porcento (176/220), p=0.05, respectivamente. As sensibilidades dos testes pan-E Dengue Early ELISA, Platelia NS1 ELISA e o NS1 Ag Strip utilizados como uma ferramenta alternativa para o diagnóstico de dengue em fragmentos de tecidos de casos fatais (n=23) foi de 34,7 porcento (08/23), 60,8 porcento (14/23) e 91,3 porcento (21/23), respectivamente...

In this context, the goal of this study was to evaluate the performance and alternative applications of NS1 capture tests commercially available. The performance of the Platelia NS1 ELISA (BioRad Laboratories) and pan-E Early ELISA, first generation (PanBioDiagnostics) and rapid test NS1 Ag Strip (BioRad Laboratories) available in the market after the introduction of these in the country, was evaluated with a panel of 450 samples. Among the three kits analyzed, the NS1 Ag Strip test was the most sensitive (89 porcent, 197/220),followed by the Platelia NS1 ELISA (84 porcent, 184/220). The least sensitive was the pan -E Early ELISA with 72 percent (159 /220) of sensitivity. A lower sensitivity was observed in DENV-3 cases by all three kits analyzed. The comparison of two generations of the NS1 Ag capture ELISA from PanBio Diagnostics (pan-E Dengue Early ELISA and Early ELISA Dengue, secondgeneration) after a test improvement by the manufacturer, showed a significant increase in the sensitivity, from 72.3 percent (159 /220) to 80 percent (176/220), p=0.05, respectively...

Dengue virus type 4 in Niterói, Rio de Janeiro: the role of molecular techniques in laboratory diagnosis and entomological surveillance

In Niterói, state of Rio de Janeiro, dengue virus type 4 (DENV-4) was isolated for the first time in March 2011. We analysed the laboratory findings of the first cases and evaluated the use of molecular techniques for the detection of DENV-4 in Aedes aegypti that were field-caught. Conventional reverse transcriptase-polymerase chain reaction (RT-PCR) and SimplexaTM Dengue real-time RT-PCR confirmed DENV-4 infection in all cases. Additionally, DENV-4 was confirmed in a female Ae. aegypti with 1.08 x 10³ copies/mL of virus, as determined by quantitative real-time RT-PCR. This is the first time the SimplexaTM Dengue real-time assay has been used for the classification of cases of infection and for entomological investigations. The use of these molecular techniques was shown to be important for the surveillance of dengue in humans and vectors.