Absolute Copy Number and Relative Change in Determinations of Human Immunodeficiency Virus Type 1 RNA in Plasma: Effect of an External Standard on Kit Comparisons

Use of a common set of human immunodeficiency virus type 1 (HIV-1) RNA standards eliminated differences among absolute HIV-1 RNA copy number estimates made with three commercially available assays. The relative changes in the viral RNA levels determined by the commercial assays were similar and were unaffected by the use of a common set of standards.