Multicenter Study of the LCx® HIV RNA Quantitative Assay – a New Competitive Reverse Transcriptase-PCR which Targets pol Genomic Region of HIV-1 for the Measurement of Type B, Non-Type B and Group O HIV-1 RNA

Abstract

Performance characteristics of the Abbott LCx HIV RNA Quantitative Assay (LCx HIV) were established in a multicenter study comparing it with the manual (Amplicor v1.5) and automated (Cobas) ultra-sensitive Roche Amplicor HIV-1 Monitor v1.5, the Bayer Quantiplex HIV RNA 3.0 (bDNA v3.0), and the Organon NucliSens HIV QT 2.0 (NucliSens). Within-run precision of LCx HIV assessed in clinical specimens was SD log10 0.210 at approximately 50 copies/ml, and log10 0.133 at approximately 400 copies/ml. Total precision in a reconstituted type B HIV-1 RNA panel was SD log10 0.380 at 100 copies/ml, and SD log10 0.180 at 1000 copies/ml. Type B HIV-1 RNA sensitivity (1 ml input) assessed at a 50%, 75% and 95% detection rate ranged from 29 to 41, 54 to 75 and 94 to 176 copies/ml, respectively. Overall specificity in HIV seronegative individuals was 99.78%. Linear regression indicated close assay correlations and agreements for measurement of type B HIV-1 RNA. Pearson's correlations and (Log10LCx=aLog10x + b) linear regressions were 0.91 (y=0.892 Log10Amplicor + 0.595), 0.93 (y=0.827 Log10Cobas + 0.969), 0.93 (y=0.951 Log10bDNA + 0.550), and 0.79 (y=0.834 Log10NucliSens + 0.911). LCx HIV was least affected by the genetic variability of HIV-1. LCx HIV detected 99% of non-type B HIV-1 group M samples (subtypes A-G), Amplicor v1.5 detected 96%, and bDNA v3.0 detected 99%. The assays detected 10/11, 1/11 and 8/11, respectively of the HIV-1 group O samples. LCx HIV vs. Amplicor/bDNA Spearman's rank correlations for quantification of non-type B HIV-1 RNA were 0.76/0.84 (A), 0.93/0.93 (C), 0.73/0.99 (D), 0.86/0.98 (E), and 0.40/0.83 (group O). LCx HIV assays consistently detect and quantify type B, non-type B and group O HIV-1 RNA.

Impact of Human Immunodeficiency Virus Type 1 (HIV-1) Genetic Diversity on Performance of Four Commercial Viral Load Assays: LCx HIV RNA Quantitative, AMPLICOR HIV-1 MONITOR v1.5, VERSANT HIV-1 RNA 3.0, and NucliSens HIV-1 QT

“…Overall, viral load values in the Monitor v1.5 and LCx assays tended to run slightly higher (0.2 to 0.3 log 10 ) than those in the bDNA assay. Similar results have been observed in previous studies (6,8,31,47).…”

“…It was the only assay that quantified all members of the panel. This is consistent with several previous reports indicating that LCx performs well on genetically diverse strains of HIV-1 (12,42,43,47). However, genetic polymorphisms can influence LCx performance, as exemplified by one panel member, a G/G/A recombinant that that was underquantified by Ͼ1.0 log 10 relative to bDNA and Monitor v1.5.…”

“…Moreover, Monitor v1.5 underquantified (Ͼ1.0 log 10 ) two additional CRF02_AG specimens and one subtype A sample. These results are consistent with previous studies where Monitor v1.5 failed to detect or significantly underquantified some strains classified within subtypes A, D, and CRF02_AG (2,35,47). Thus, although performance of the Monitor v1.5 assay on non-B subtype viruses is markedly improved relative to that of the Monitor v1.0 assay (29,42,43,46), specific strains within several subtypes and CRFs may be underquantified.…”

“…The somewhat reduced correlations observed in the present study likely reflect the genetically diverse panel. In studies where performance with non-subtype B virus isolates was examined, correlations and agreement between assays were reduced, comparable with our results (6,8,12,42,43,47). Overall, viral load values in the Monitor v1.5 and LCx assays tended to run slightly higher (0.2 to 0.3 log 10 ) than those in the bDNA assay.…”

Comparison of LCx with Other Current Viral Load Assays for Detecting and Quantifying Human Immunodeficiency Virus Type 1 RNA in Patients Infected with the Circulating Recombinant Form A/G (CRF02)

“…Although the LCx assay employs primers targeting a specific and highly conserved sequence in the pol region, ensuring consistent results for all HIV-1 M and O subtypes (26), this study demonstrated a certain degree of inability to efficiently quantificate VL from CRF02. This inability is less pronounced than that previously demonstrated for Nuclisens (27).…”