673
Non-NAT-based Virological Marker as a Potential Alternative to Nat-based Plasma Viral Load for Monitoring ART in Resource-limited Settings
Syed Iqbal*1, P Balakrishnano1, S Solomon1, A Cecelia1, N Kumarasamy1, V Madhavan1, M Kg1, K Mayer2, and S Crowe3
1YRGCARE, Chennai, India; 2Brown Univ, The Miriam Hosp, Providence, RI, US; and 3The Macfarlane Burnet Inst for Med Res and Publ Hlth, Melbourne, Australia
Background: The
clinical management of HIV patients is based mainly on CD4+ T-lymphocyte
cell count and plasma viral load.
Particularly, plasma viral load plays a major role after initiating ART
for better clinical outcome. The nucleic acid–based viral load assays (NAT)
require infrastructure facilities and skilled personnel and they are expensive.
An inexpensive and technically less-demanding method to quantify HIV-1 would be
of great value for settings where NAT is impractical or resource
prohibitive. The present study compares
the performance of non-NAT-based ExaVir load RT assay with standard (RNA polymerase
chain reaction [PCR]) Roche HIV-1 Monitor assay.
Methods: For the
evaluation, we used 121 plasma specimens from 107 HIV-infected patients. The HIV-1 reverse transcriptase enzyme
activity assay (ExaVir Load Assay, version 1.0) as non-NAT was compared with
the “gold standard” assay, Roche HIV-1 Monitor, version 1.5 assay. Bland-Altman
analysis was performed and sensitivity, specificity, positive predictive value,
and negative predictive value were determined for the clinically critical
limits. The negative correlation between CD4+ T cell and ExaVir load
were analyzed using Pearson’s correlation coefficient.
Results: The sensitivity of ExaVir load assay to detect <400
copies/mL equivalent to <5500 was 100%. Also, the specificity of detecting >400
copies/mL in standard PCR when compared to ExaVir Load at >5500 was 72%. The
difference (95% limits of agreement) seen in ExaVir Load when compared to standard
PCR was –0.23 copies/mL (0.45 to –0.91) on the logarithmic scale using the
Bland-Altman analysis. CD4+ T-cell
counts estimated by flow cytometry and log10 copies/mL of ExaVir
load assay were negatively correlated and was statistically significant (r = 0.32, p = 0.028).
Conclusions: The
present study with subtype C has shown a strong correlation between the
non-NAT-based ExaVir RT assay and the standard PCR assay. Hence, ExaVir load
assay, after further evaluation with prospective specimens, could be considered
for use in resource-limited settings as an alternative viral load assay to the
standard NAT-based assay.
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