Evaluation of two fourth-generation screening assays for the detection of HIV-1/2 in dried blood spots
Objectives: There is an urgent need for simple and highly sensitive HIV screening assays suitable to resource-limited settings. Dried blood spot (DBS) is a reliable method for the collection, transport and storage of samples while fourth-generation EIAs (FGEIA) detect HIV Ab and p24 Ag simultaneously offering greater sensitivity and a shorter window of detection. Combined these systems can improve HIV testing access and performance. We aimed to evaluate two commercially available FGEIAs using a modified protocol for DBS specimens stored for short and long periods.
Methods: Two reference HIV panels were obtained from blood donors and HIV patients in southern Brazil. Fifty microliters whole blood–EDTA specimens were transferred to filter paper (S&S 903) and dried and stored at room temperature in zip-lock bags with desiccant for a period of 6 to 15 weeks (short-term=ST) and 17 to 34 weeks (long-term=LT). DBS was screened for the presence of HIV 1/2 by Genscreen Plus HIV Ag/Ab (Biorad) and Murex HIV Ag/Ab Combination (Abbot). DBS was eluted empirically using the same protocol for both assays and tested according to the manufacturer´s instruction. Performance characteristics were calculated using the reference panel.
Results: For ST (HIV- (n=43); HIV+ (n=62)) Genscreen resulted in a sensitivity (Se) 100% (95%CI 92.7-100%); specificity (Sp) 88.3% (95%CI 74.1-99.5%). ST Murex, (HIV- (n=44); HIV+ (n=49)): Se 100% (95%CI 90.9-100%); Sp 88.6% (95%CI 74.6-95.7%). For LT (HIV- (n=192); HIV+ (n=92), Genscreen maintained its performance. LT Murex, (HIV- (n=42); HIV+ (n=39); had optimal Se but poor Sp (11.9% (95%CI 4.4-26.4%).
Conclusions: FGEIA kits can be modified for use with DBS stored for up to 15 weeks, are easy to perform and use equipment found in most laboratories. Definition of elution protocols needs to be tailored to each FGEIA kit to avoid problems with low specificity.
da Silva de Souza R.1, Borges L.G.1, Motta L.1, de Souza D.2, do Amaral Inocêncio L.2
Universidade de Caxias do Sul - Laboratório de Pesquisa em HIV/AIDS