Dried blood spots (DBS) and dried plasma spots (DPS) collected on filter papers are suitable for the quantification of HIV-1 viral load (VL) in patients receiving antiretroviral therapy (ART) in resource constrained settings
K. Diallo1, E. Lehotzky1, J. Zhang1, I. Lorenzana de Rivera2, W.E. Murillo2, V. Shanmugam1, J. Nkengasong1, J. Sabatier3, C. Yang1
1Centers for Disease Control and Prevention, International Laboratory Branch, Division of Global AIDS, CGH, Atlanta, United States, 2National Autonomous University of Honduras, Microbiology, Tegucigalpa, Honduras, 3Centers for Disease Control and Prevention, Strategic Information Branch, Global AIDS Program, CGH, Atlanta, United States
Background: VL measurement is useful in monitoring the development of drug resistance in patients receiving ART. Evidence shows that DBS can produce incorrect higher results, particularly when VL is low. We evaluated DBS performance collected on newly designed Whatman FTA cards along with DPS and DBS collected on Whatman 903 cards for VL determination.
Methods: In Honduras, left over whole blood from 79 ART patients was used to prepare DBS and DPS using FTA and 903 cards. The remaining plasma was frozen to be used as gold standard (GS). Cards were stored at room temperature (RT) for either 2 or 4 weeks. DBS and DPS nucleic acid was extracted using Biomerieux EasyMAG and VL measured with EasyQ v1.1. Detection limit is 50 copies/mL of plasma. VL of GS was determined using Roche Amplicor HIV-1 Monitor, v1.5. Detection limit is 400 copies/mL of plasma.
Results: Undetectable VL for GS and DBS/DPS were equivalent. Bland Altman plots constructed for detectable samples indicate acceptable agreement between methods. Correlation analysis on Bland-Altman transformed data indicates no bias. For Bland-Altman analysis, a low correlation and a high p-values (>0.05)
indicate agreement.(Table 1).
Conclusions: DBS and DPS on Whatman FTA and 903 cards VL were in agreement to GS and these data suggest Whatman 903 and FTA cards are suitable for DBS/DPS collection to determine VL. Storage conditions including RT for either 2 or 4 weeks had no detectable effect on VL values.
[Bland Altman R-square,Correlation and P-values]
|Parameters||GS-plasma vs. DBS/2 weeks||GS-plasma vs. DBS/4 weeks||GS-plasma vs. DPS/2 weeks||GS-plasma vs. DPS/4 weeks||GS-plasma vs. FTA/2 weeks||GS-plasma vs. FTA/4 weeks|
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