7 We invited healthy children residing in Bogo and Balamban, semi-urban areas in Cebu, who would be 9–14 years of age at the time of the dengue mass vaccination to participate in the study. We initiated a prospective cohort study just before the mass dengue vaccination in Cebu Province. The Philippine government launched a dengue mass immunization in 2016 in high-risk regions using the first licensed dengue vaccine, CYD-TDV (Dengvaxia, Sanofi Pasteur, Lyon, France). Study participants and sample collection. 8 We evaluated the performance of DBS as the index test compared with sera as the reference standard in the detection of previous DENV infection by dengue IgG ELISA. Because blood volumes on DBS are small and the stability of the samples in a filter paper is uncertain, there is a need for rigorous assay validation compared with standard methods. 7 The ELISA with a 0.9 index value cutoff was 95.2% sensitive and 93.4% specific with a 6.6% false positivity and 4.8% false negativity compared with neutralization testing in the detection of dengue seropositivity.Ĭompared with sera, the use of dried blood spots (DBS) allows easier sample collection, shipment, transport, and storage, thus increasing accessibility of dengue serosurveys to rural areas and low-resource settings. 5 We previously validated a dengue IgG indirect ELISA (PanBio, Brisbane, Australia) by neutralization testing using sera from healthy children in Cebu, Philippines. 6 The less sensitive and specific but easier to perform indirect IgG ELISA has been recommended for population serosurveys, ideally with a subset validated by neutralization testing. The generally accepted reference standard for detecting anti-DENV antibodies from previous natural infection is neutralization testing of sera, but this method is time and labor intensive and only available in research settings. In addition, dengue seroprevalence data may also inform decisions on implementation or intensification of dengue control programs. 4 Dengue seroprevalence data stratified by time, location, and age-group are useful for understanding seasonal and annual trends, spatial range, high-risk populations, and transmission dynamics. 2, 3 Population-based serological surveys are an effective tool to determine the distribution and impact of dengue. Clinically apparent cases may be as low as 25% of total infections. Estimates of symptomatic disease incidence provide important insights on the burden of dengue, 1 but they are incomplete because of variable healthcare-seeking behavior and subclinical infections. Considering the advantages in terms of sample collection, shipment, and storage, DBS sampling may be appropriate for dengue population serosurveys.ĭengue fever is a mosquito-borne, acute febrile illness caused by four antigenically distinct dengue virus (DENV) serotypes, DENV-1 to 4. Compared with sera, the DBS method had a 98.3% sensitivity, 92.4% specificity, 98.9% positive predictive value, and 89.2% negative predictive value. Using an ELISA index value cutoff of 0.9, 1,285/1,488 (86.4%) of the DBS were seropositive and 203 (13.6%) were seronegative, compared with 1,292/1,488 (86.8%) seropositive and 196 (13.2%) seronegative serum samples. Specimens were collected from healthy children in Cebu, Philippines, who would be 9–14 years of age at the time of a mass dengue vaccination program. We evaluated the detection of anti-dengue antibodies by IgG indirect ELISA when using DBS compared with sera. Further evidence is needed to understand how well DBS performs compared with standard serum collection methods in laboratory assays. For conducting large and repeated dengue serosurveys, dried blood spots (DBS) would allow easier sample collection, shipment, transport, and storage than standard serum collection methods. A logistical challenge to seroprevalence surveys is the collection and transport of serum samples. Dengue seroprevalence data are useful for understanding epidemiologic trends and transmission dynamics, and for making decisions about implementation of dengue control programs.
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