title: Blood screening for human immunodeficiency virus: a new algorithm to reduce the false-positive results.
abstract: OBJECTIVE
  The objectives to this study were to evaluate the performance of an anti-human immunodeficiency virus (HIV) blood screening test and propose a new screening algorithm for blood banks routinely using nucleic acid amplification testing (NAT) to reduce false-positive results.
  
  
  BACKGROUND
  Most anti-HIV enzyme-linked immunosorbent assay (ELISA) results are false-positive because of the low prevalence of HIV infection and high sensitivity of the ELISAs.
  
  
  METHODS
  A total of 281 588 voluntary donations were collected and sera reactive on one or both anti-HIV ELISAs were confirmed by Western blot (WB) testing. All samples with nonreactive results for the two ELISAs underwent NAT. A confirmed HIV-1-positive result was defined by a reactive result on NAT or WB testing. Correlations between signal-to-cutoff ratios and the confirmed HIV-1 infection rate were analysed for each enzyme immunoassay and two-enzyme immunoassay combination. The positive predictive values (PPVs) of the current and proposed algorithms were calculated.
  
  
  RESULTS
  Seventy-nine donations (13·9%) were positive on WB analysis and one donation negative for anti-HIV antibody was reactive on NAT and confirmed to be a window period donation on additional follow-up testing. The PPV of the 567 donations reactive on one or two ELISAs was 13·9%. However, using the new screening algorithm, 457 donations underwent NAT immediately instead of WB testing. Only 110 donations were tested with WB and the PPV was 71·8%.
  
  
  CONCLUSIONS
  Screening for HIV is sensitive, specific and time saving for donors with this algorithm, which is suitable for HIV screening in low prevalence settings.
authors: National Center for Clinical Laboratories, Beijing Hospital of the Ministry of Health, Beijing, People's Republic of China.
authors: R
authors: R
authors: Zhang
authors: Y
authors: Y
authors: Sun
authors: L
authors: L
authors: Wang
authors: K
authors: K
authors: Zhang
authors: J
authors: J
authors: Xie
authors: J
authors: J
authors: Li
mesh_terms: D000465:Algorithms; D015153:Blotting, Western / Q000379:methods; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005189:False Positive Reactions; D005260:Female; D015483:HIV Antibodies / Q000097:blood*; D015658:HIV Infections / Q000097:blood*; D015497:HIV-1; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000379:methods*; D012680:Sensitivity and Specificity
chemical_list: D015483:HIV Antibodies
keywords: anti-HIV; cut-off ratio; enzyme-linked immunosorbent assay; false-positive results