title: Reliability at the lower limits of HIV-1 RNA quantification in clinical samples: a comparison of RT-PCR versus bDNA assays.
abstract: BACKGROUND
  To explore whether an assay change was responsible for an increasing proportion of patients with undetectable HIV viral loads at our urban HIV clinic, we selected highly stable patients, examining their viral loads before and after changing assays. We compared the proportion with detectable viremia during RT-PCR vs. bDNA periods.
  
  
  RESULTS
  We selected patients with > or =1 viral loads assessed during both RT-PCR and bDNA periods. We included patients with stable CD4 counts, excluding patients with viral loads > or =1,000 copies/ml or any significant changes in therapy. Out of 4500 clinic patients, 419 patients (1588 viral loads) were included. 39% of viral loads were reported as detectable by RT-PCR vs. 5% reported as detectable by bDNA. The mean coefficient of variation was higher before vs. after assay change. We found an odds' ratio of 16.7 for having a viral load >75 copies/ml during the RT-PCR vs. bDNA periods.
  
  
  CONCLUSIONS
  These data support previous reports, suggesting that bDNA may more reliably discriminate between viral suppression and low level viremia in stable patients on therapy. Low-level viremia, noted more with RT-PCR, may promote unneeded testing, while differences in viral load reliability may impact antiretroviral trial and quality assurance endpoints. Commonly used plasma separator tubes may differentially affect RT-PCR and bDNA results.
authors: Division of Infectious Diseases, John H Stroger, Jr Hospital of Cook County, Chicago, IL, USA. rlubel@gmail.com
authors: Ronald J
authors: RJ
authors: Lubelchek
authors: Blake
authors: B
authors: Max
authors: Caroline J
authors: CJ
authors: Sandusky
authors: Bala
authors: B
authors: Hota
authors: David E
authors: DE
authors: Barker
mesh_terms: D000328:Adult; D021121:Branched DNA Signal Amplification Assay / Q000379:methods*; D015704:CD4 Antigens / Q000096:biosynthesis; D015331:Cohort Studies; D005260:Female; D015658:HIV Infections / Q000175:diagnosis* / Q000235:genetics; D015497:HIV-1 / Q000235:genetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012367:RNA, Viral; D015203:Reproducibility of Results; D012189:Retrospective Studies; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods*; D019562:Viral Load / Q000379:methods*; D014766:Viremia / Q000175:diagnosis* / Q000235:genetics
chemical_list: D015704:CD4 Antigens; D012367:RNA, Viral