B-042 Performance evaluation of Atellica IM infectious disease assays with dried blood spot sample

Abstract

Background Dried Blood Spots (DBS) have been used for screening of inherited metabolic disorders in newborns and infectious disease in key populations (intravenous drug users, homeless, and sex workers) due to ease of blood collection and transportation. Siemens Healthineers Atellica IM CHIV, HBsII, and HBcT2 assays are commercially available fully automated assays for the diagnosis of HIV and HBV infection in serum and plasma. To enhance widespread detection of HIV and HBV infected individuals, performance of Atellica IM CHIV, and HBcT2 assays is evaluated with DBS. Methods To determine optimal conditions for use of DBS, blood spot drying time, punch size, and elution conditions (buffer, time, and mixing method) studies were conducted. The initial studies were conducted with dried plasma spots and subsequently verified with blood spots. For Atellica IM assays performance evaluation with DBS, blood was collected from normal donors and spiked with respective analytes. The Whatman 903 filter card was spotted with 50 ul of spiked or unspiked blood from each donor. The remaining blood was centrifuged to obtain plasma. For DBS elution, the punched spots were eluted in selected elution buffer. The DBS eluates and matched plasma were tested with Atellica IM CHIV, and HBcT2 assays using standard assay parameters. The results were analyzed using assay cut-off as per IFU. The results were also analyzed with DBS specific cut-off derived from results obtained with unspiked DBS samples. Results DBS drying time >2 hours did not show improvement in analyte recovery. For DBS elution, testing of 1-3 spots in 500 µl elution buffer showed increase in recovery with increasing spots. When 6 mm and 12 mm punches from 2 spots were compared, the latter provided enhanced recovery. Among tested conditions, elution of 2 spots in 500 ul of Atellica IM Wash buffer at room temperature with shaking for 2 hours showed optimal recovery. Using these conditions, DBS and plasma of unspiked blood from 27–30 donors were tested with Atellica IM CHIV, and HBcT2 assays. All DBS samples and matched plasma were nonreactive with all 3 assays using respective commercial cut-off (1 index). When DBS and plasma of HIV-1, HIV-2, Group ‘O’ and p24 spiked blood were tested with CHIV assay, DBS showed 5 to 10-fold lower dilutional sensitivity compared to plasma using commercial cut-off. Reduced dilutional sensitivity was observed in DBS with HBsII assay (8-fold lower) and HBcT2 assay (20-fold lower) with commercial cut-offs. The results from unspiked donors were used to calculate a DBS specific cut-off (Avg + >=7SD). With DBS specific cut-offs (CHIV-0.51 index, HBsII-0.31 Index, HBcT2-0.46 Index), all the unspiked donor DBS samples were nonreactive with all 3 assays showing 100% specificity. DBS dilutional sensitivity was significantly improved with DBS specific cut-offs. The HBsII and HBcT2 assays showed dilutional sensitivity 2-fold lower and CHIV assay showed 2-5-fold lower compared to plasma. Conclusions These results demonstrate that comparable performance of Atellica IM CHIV, and HBcT2 assays with DBS can be achieved. In Development. Not commercially available. Future availability cannot be guaranteed.