Automated and combined HIV, HBV, HCV, and syphilis testing among illegal gold miners in French Guiana using a standardized dried blood device.

Abstract: Background: Blood spotted onto filter paper can be easy collected outside healthcare facilities and shipped to central laboratory for serological testing. However, dried blood testing generally request manual processing for elution. In this study, we used a standardized blood collection device combined with an automatized elution system to test illegal gold miners living in French Guiana for HIV, HBV, HCV and syphilis. Material and Methods: We included 378 participants in five resting sites of illegal gold mining. Serological status was determined by testing serum samples. Blood collected on the Ser-Col device (Labonovum), was eluted using an automated system (SCAUT Ser-Col automation, Blok System Supply) and an automatized analyzer (Alinity i, Abbott). Ser-Col results were compared to serum considered as the reference, and dried blood spot samples processed manually. Results: Two participants tested positive for HIV (0.5%), eight tested positive for hepatitis B surface antigen (HBsAg), four tested low positive for anti-HCV antibodies (1%) but negative for HCV RNA, 47 tested positive for syphilis (12.4%). We observed a full concordance of Ser-Col and DBS results for HIV diagnosis compared to serum results. Ser-Col and DBS samples tested positive in seven HBsAg carriers and negative for one participants having a low HBsAg level in serum (0.5 IU/mL). Three hundred and sixty-eight participants uninfected by HBV tested negative for HBsAg (99.5%). Two Ser-Col samples and two other DBS samples positive tested positive in HBV uninfected participants (false positive results with low S/CO indexes). All participants tested negative for HCV in Ser-Col and DBS samples, including in dried blood samples from the four participants tested low positive for HCV antibodies and HCV RNA negative in serum. The threshold of the treponemal assay was optimized for dried blood sample testing. Among syphilis seropositive participants, 35 (74.61%) tested positive for treponemal antibodies in Ser-Col and DBS samples. Among participants seronegative for syphilis, 326 (98.4%) and 325 (98.1%) tested negative in Ser-Col and DBS samples, respectively. Conclusion: The Ser-Col method allows to automatized dried blood testing of HIV, HBV, HCV and syphilis with performance comparable to DBS. Automated approaches to test capillary blood transported on dried blood devices may facilitate large scale surveys and improve testing of populations living in remote areas for infectious diseases.