Article Figures & Data
Figures
- FIG 1
Comparisons among viral load assays. (A and B) Shown is the correlation of the TaqMan assays with either the Amplicor assay (A) or the RealTime assay (B). Comparisons involving TaqMan version 1 are shown with filled gray circles, while those involving TaqMan version 2 are shown with open squares. The R2 values for all correlations are shown in the legends. (C to F) The bottom four panels show Bland-Altman difference plots comparing different viral load assays. Shown are comparisons of the Amplicor assay with the TaqMan version 1 (C) or version 2 (D) assay and of the RealTime assay with the TaqMan version 1 (E) or version 2 (F) assay. The bias (mean difference between the assays) is shown as a solid horizontal line, and the 95% limits of agreement are shown with dashed lines at ±1.96 standard deviations.
- FIG 2
Proportion of samples with <50 copies/ml by the Amplicor assay as a function of the TaqMan version 1 or version 2 assay. The proportion of samples with Amplicor results of <50 copies/ml decreased at higher TaqMan version 1 and version 2 strata. (A) Proportion of samples with undetectable viral loads by the Amplicor assay (<50 copies/ml) as a function of the viral load reported by the TaqMan version 1 assay. (B) Similar plot as in panel A but as a function of the viral load reported by the TaqMan version 2 assay. For both TaqMan assays, when either had a viral load result of up to 100 copies/ml, a majority of the corresponding samples were actually undetectable by the Amplicor assay.
Tables
- TABLE 1
Correlation coefficients for interassay comparisons at viral loads of <1,000 copies/mla
Assay detection (at <1,000 copies/ml) Correlation coefficients of discordant results of ≥1,000 copies/ml Amplicor RealTime TaqMan v1 TaqMan v2 Amplicor NAb 0.52 0.85 RealTime NA 0.74 0.82 TaqMan v1 0.45 0.54 0.69 TaqMan v2 0.80 0.78 0.68 ↵a Correlation coefficients of the interassay comparisons were calculated using the results with a restriction of at least one viral load assay giving a result of <1,000 copies/ml. The assay restricted to <1,000 copies/ml is shown in the left-hand column, and its comparator assay is indicated in the columns. For example, when TaqMan v1 was restricted to values of <1,000 copies/ml, the matching Amplicor test results had an R value of 0.45. Conversely, when the Amplicor test was restricted to <1,000 copies/ml, the matching TaqMan v1 results had an R value of 0.52.
↵b NA, not available.
- TABLE 2
Discordance for HIV-1 RNA levels at <50 copies/ml
Assay (at <50 copies/ml) % discordant results of ≥50 copies/ml (no. of discordant samples/total no. of samples)a Amplicor RealTime TaqMan v1 TaqMan v2 Amplicor NA 73 (598/819) 6 (10/172) RealTime NA 27 (63/230) 13 (73/569) TaqMan v1 11 (27/248) 23 (49/216) 24 (50/206) TaqMan v2 5 (8/170) 7 (40/356) 25 (51/207) ↵a Shown are the percentages of results that were discordant between the assays at a threshold of 50 copies/ml. NA, not available.
- TABLE 3
Discordance for HIV-1 RNA levels at <200 copies/mla
Assay (at <200 copies/ml) % discordant results of ≥200 copies/ml (no. of discordant samples/total no. of samples) Amplicor RealTime TaqMan v1 TaqMan v2 Amplicor NA 5 (58/1,161) 3 (7/204) RealTime NA 10 (37/356) 7 (49/728) TaqMan v1 7 (85/1,188) 16 (59/378) 7 (25/236) TaqMan v2 3 (7/204) 3 (22/701) 1 (3/314) ↵a Shown are the percentages of results that were discordant between the assays at a threshold of 200 copies/ml. The percentage of discordant samples decreased for all comparisons when a threshold of 200 copies/ml was used, compared to a 50-copies/ml threshold. NA, not available.
