title: The contribution of assay variation and biological variation to the total variability of plasma HIV-1 RNA measurements. The Women Infant Transmission Study Clinics. Virology Quality Assurance Program.
abstract: OBJECTIVE
  To assess the specific contributions of assay variation and biological variation to the total variation of plasma HIV-1 RNA measured by the Roche Monitor assay and the extent to which batch assays reduced both assay variability and total variability compared with real-time determinations.
  
  
  METHODS
  A retrospective analysis of data obtained from three trials conducted by the Adult and Pediatric AIDS Clinical Trials Groups (ATCG), the Women and Infants Transmission Study (WITS) and the NIAID-sponsored Virology Quality Assurance Program.
  
  
  METHODS
  Within-subject variation was assessed from stored, serially collected plasma samples from 663 subjects enrolled in the ACTG and WITS studies. Interassay and intra-assay variation were estimated from two of the clinical trials and 22 laboratories that participated in a quality assurance program and were used to estimate the effect of real-time testing on total variation.
  
  
  RESULTS
  The total variation (standard deviation) from a random effects model was 0.26 log10 RNA copies/ml. The estimated interassay variation was 0.08 log10 and intra-assay variation was 0.12 log10 RNA copies/ml. Biological variation accounted for 56-80% of total variation. The effect of real-time testing compared with batch testing was minimal.
  
  
  CONCLUSIONS
  Our estimates of total within-subject HIV-1 RNA variation support the current recommendation to obtain at least two specimens, preferably obtained less than 2 weeks apart, for viral RNA measurement before starting therapy. The major contribution of biological variation to the total variation supports the use of real-time HIV-1 RNA assays, provided that consistent specimen collection procedures are followed and acceptable assay proficiency is maintained.
authors.affiliation: New England Research Institute, Watertown, MA 02472, USA.
authors.forename: D
authors.initials: D
authors.lastname: Brambilla
authors.forename: P S
authors.initials: PS
authors.lastname: Reichelderfer
authors.forename: J W
authors.initials: JW
authors.lastname: Bremer
authors.forename: D E
authors.initials: DE
authors.lastname: Shapiro
authors.forename: R C
authors.initials: RC
authors.lastname: Hershow
authors.forename: D A
authors.initials: DA
authors.lastname: Katzenstein
authors.forename: S M
authors.initials: SM
authors.lastname: Hammer
authors.forename: B
authors.initials: B
authors.lastname: Jackson
authors.forename: A C
authors.initials: AC
authors.lastname: Collier
authors.forename: R S
authors.initials: RS
authors.lastname: Sperling
authors.forename: M G
authors.initials: MG
authors.lastname: Fowler
authors.forename: R W
authors.initials: RW
authors.lastname: Coombs
mesh_terms: D000328:Adult; D019380:Anti-HIV Agents / Q000627:therapeutic use; D002986:Clinical Trials as Topic; D016001:Confidence Intervals; D005260:Female; D015658:HIV Infections / Q000188:drug therapy / Q000821:virology*; D015497:HIV-1 / Q000235:genetics / Q000302:isolation & purification*; D006801:Humans; D008297:Male; D012367:RNA, Viral / Q000097:blood*; D012189:Retrospective Studies
chemical_list: D019380:Anti-HIV Agents; D012367:RNA, Viral