Evaluation of the performance of Abbott m2000 and Roche COBAS Ampliprep/COBAS Taqman assays for HIV-1 viral load determination using dried blood spots and dried plasma spots in Kenya

Abstract

BackgroundRoutine HIV viral load testing is not widely accessible in most resource-limited settings, including Kenya. To increase access to viral load testing, alternative sample types like dried blood spots (DBS), which overcome the logistic barriers associated with plasma separation and cold chain shipment need to be considered and evaluated. The current study evaluated matched dried blood spots (DBS) and dried plasma spots (DPS) against plasma using the Abbott M 2000 (Abbott) and Roche Cobas Ampliprep/Cobas TaqMan (CAP/CTM) quantitative viral load assays in western Kenya.MethodsMatched plasma DBS and DPS were obtained from 200 HIV-1 infected antiretroviral treatment (ART)-experienced patients attending patient support centers in Western Kenya. Standard quantitative assay performance parameters with accompanying 95% confidence intervals (CI) were assessed at the assays lower detection limit (400cps/ml for CAP/CTM and 550cps/ml for Abbott) using SAS version 9.2. Receiver operating curves (ROC) were further used to assess viral-load thresholds with best assay performance (reference assay CAP/CTM plasma).ResultsUsing the Abbott test, the sensitivity and specificity, respectively, for DPS were (97.3%, [95%CI: 93.2–99.2] and 98.1% [95%CI: 89.7–100]) and those for DBS (93.9% [95%CI: 88.8–97.2] and 88.0% [95%CI: 82.2–92.4]). The correlation and agreement using paired plasma and DPS/DBS were strong, with r2 = 90.5 and rc = 68.1. The Bland-Altman relative percent change was 95.3 for DPS, (95%CI: 90.4–97.7) and 73.6 (95%CI: 51.6–86.5) for DBS. Using the CAP/CTM assay, the sensitivity for DBS was significantly higher compared to DPS (100.0% [95% CI: 97.6–100.0] vs. 94.7% [95%CI: 89.8–97.7]), while the specificity for DBS was lower: 4%, [95% CI: 0.4–13.7] compared to DPS: 94.0%, [95% CI: 83.5–98.7]. When compared under different clinical relevant thresholds, the accuracy for the Abbott assay was 95% at the 1000cps/ml cut-off with a sensitivity and specificity of 96.6% [95% CI 91.8–98.7] and 90.4% [95% CI 78.2–96.4] respectively. The optimum threshold was at 3000 cps/ml with an accuracy of 95.5%, sensitivity and specificity of 94.6% [95%CI 89.3–97.5] and 98.1% [95%CI 88.4–99.9]) respectively. The best threshold for CAP/CTM was at 4000 copies /mL, with 92.5% accuracy (sensitivity of 96.0% [95%CI 91.0–98.3] and specificity of 82.7% [95%CI 69.2–91.3]).ConclusionsThere was similar performance between matched DBS, DPS and plasma using the Abbott test, and good correlation for matched DPS and plasma using the CAPCTM test. The findings suggest that DBS and DPS may be reliably used as alternative specimens to plasma to measure HIV-1 VL using Abbott, and DPS may be reliably used with CAP/CTM in resource-limited settings.

Whatman FTA®cards versus plasma specimens for the quantitation of HIV-1 RNA using two Real-Time PCR assays

“…This observation of discrepant results is consistent with findings from other studies using Whatman 903 ® cards [15,21–23]. The reasons of these discrepant results were well documented in the literature[15,17,21–23]. In a systematic review published in 2014, Smit et al [17] have indicated that the most important reasons DBS is not, and may never be, as sensitive as plasma is because of the differences in sample volume between DBS and plasma.…”

“…However, in this study, 17.0% samples tested not detected on FTA cards, were positive on plasma specimens, with 2.1% high positive. This observation of discrepant results is consistent with findings from other studies using Whatman 903 ® cards [15,21–23]. The reasons of these discrepant results were well documented in the literature[15,17,21–23].…”

“…Both Roche and Abbott assays in this study showed a good correlation and agreement between FTA cards and plasma values which is similar to other studies comparing DBS (using Whatman 903 ® cards) to plasma specimens with Roche and Abbott assays [12,14,15,20].…”

“…At the clinical threshold of 1000 copies/mL, sensibility of FTA cards in this study was seen at 78.6% with Roche, which was slightly less than that observed with Abbott assay (Se = 92.3%) and in already most available literature using Whatman 903 ® cards [15,21–24,28]. Inversely, our results were higher than that observed in Vietnam using Whatman 903 ® cards with Roche assay [29].…”

Adherence Measurements in HIV: New Advancements in Pharmacologic Methods and Real-Time Monitoring

“…Likewise, DBS samples can be stored for relatively long periods of time after collection and can be shipped without special biohazard precautions[24, 30]. These advantages have led to the use of DBS sampling for analysis beyond the neonatal period, including rapid diagnostics of vector-borne diseases[31], identification of disease-associated genetic mutations[32], diagnosis of HIV infection, and quantification of HIV VL[33–36], among others.…”