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5th International AIDS Society Conference on HIV Pathogenesis and TreatmentCape Town - July 19 - 22, 2009 |
SEMI-QUANTIFICATION OF THE APTIMA HIV-1 SCREENING ASSAY WITH GEN-PROBES' HIGH THROUGHPUT TIGRIS ANALYSER FOR APPLICATION IN SUBTYPE C HIV-1 VIRAL LOAD MONITORING
IAS Conf HIV Pathog Treat 2009 Jul 19-22;5th: Abstract No. MOPDB102
L.E. Scott
1, L. Berrie2, P. Horsfield3, W.S. Stevens3,4
1University of the Witwatersrand, Molecular Medicine and Haematology, Johannesburg, South Africa, 2ILEX, Johannesburg, South Africa, 3University of the Witwatersrand, Johannesburg, South Africa, 4The National Health Laboratory Service, Johannesburg, South Africa
BACKGROUND: The Gen-Probe APTIMA HIV-1 Screening assay is a qualitative nucleic acid test based on the Procleix Discriminatory technology from Chiron(San Francisco) routinely used in South African Blood banks with the TIGRIS high throughput platform (~1000samples/14hrs). The sensitivity of this assay for infant HIV diagnosis on whole blood (and DBS) was recently determined to be 100%, with 99.4% specificity. We investigated whether the signal/cut off (S/CO) ratio can predict viral load (VL) for high throughput monitoring in subtype C.
METHODS: 109 plasma samples (1ml) were analysed on the APTIMA HIV-1 Screening assay using the TIGRIS platform and S/CO ratios were compared to the mean VL obtained from three real time VL monitoring assays: Abbott HIV-1 RealTime(Abbott), CAP/CTM HIV-1 (Roche), NucliSENS HIV-1 (bioMerieux). Correlation (r) and linear regression (including R2) were applied.
RESULTS: There were 60 LDL (non-quantifiable) samples with S/CO of 0.07-19.61. The mean VL from 49 quantifiable samples was Log 4.9 (Log1.97-Log6.22c/ml) and their S/CO ranged from 13.5-32.15. There was a significant (p<0.0001) correlation (r=0.663) between S/CO and VL, but the coefficient of determination (R2) showed only 44% of the data pairs represented by the equation y=2.37x+14.33. Sorting the S/CO into 4VL categories (Figure 1), showed all samples with S/CO< 20 had VL< 700c/ml (Log2.85) and S/CO>20 yielded values >723c/ml (except 1 sample).
CONCLUSION: In this study, the APTIMA HIV-1 Screening assay could be used to determine semi-quantitative VL categories facilitating high throughput screening for ARV treatment switches. This semi-quantitative cut off requires further clinical validation.
2009-07-22
MOPDB102
Poster Discussion MOPDB1 - Update on Diagnosing and Monitoring
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