Diagnostic accuracy of ultrasensitive heat-denatured HIV-1 p24 antigen in non-B subtypes in Kampala, Uganda

L. A. Spacek, F. Lutwama, H. M. Shihab, J. Summerton, M. R. Kamya, A. Ronald, O. Laeyendecker, T. C. Quinn, H. Mayanja-Kizza

Research output: Contribution to journalReview articlepeer-review

5 Scopus citations


We evaluated the accuracy of heat-denatured, amplification-boosted ultrasensitive p24 assay (Up24) compared with reverse transcriptase polymerase chain reaction (RT-PCR). We tested 394 samples from Ugandans infected with HIV-1 non-B subtypes. We compared Up24 levels (HIV-1 p24 Core Profile enzyme-linked immunosorbent assay (ELISA), NEN Life Science Products) to RNA viral loads (Amplicor HIV-1 Monitor 1.5, Roche) by linear regression, and calculated sensitivity, specificity, positive and negative predictive values. Median viral load was 4.9 log10 copies/mL (interquartile range [IQR], 2.6-5.5); 114 samples (29%) were undetectable (<400 copies/mL). Sensitivity of the Up24 assay to detect viral load ≥400 copies/mL was 69%, specificity was 67%, and positive and negative predictive values were 84% and 47%, respectively. Sensitivity of Up24 was 90%, 80%, 68%, 62% and 45% to detect viral loads of >500,000, 250,000-500,000, 100,000-250,000, 50,000-100,000 and 400-50,000 copies/mL, respectively. In conclusion, when compared with RT-PCR for patients infected with non-B subtypes, the Up24 demonstrated limited sensitivity especially at low viral loads. Moreover, the Up24 was positive in 33% of samples deemed undetectable by RT-PCR, which may limit the use of the Up24 to detect viral suppression.

Original languageEnglish (US)
Pages (from-to)310-314
Number of pages5
JournalInternational Journal of STD and AIDS
Issue number6
StatePublished - Jun 2011
Externally publishedYes


  • Africa
  • Diagnosis
  • HIV
  • Monitoring ART
  • Non-B subtypes
  • Resource-limited setting
  • Sensitivity
  • Specificity
  • Uganda
  • Ultrasensitive HIV-1 p24 assay
  • Viral load

ASJC Scopus subject areas

  • Dermatology
  • Public Health, Environmental and Occupational Health
  • Pharmacology (medical)
  • Infectious Diseases


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