title: Diagnostic accuracy of ultrasensitive heat-denatured HIV-1 p24 antigen in non-B subtypes in Kampala, Uganda.
abstract: 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.
authors.affiliation: Johns Hopkins Medical Institutions, Baltimore, MD 21287, USA. lspacek@jhmi.edu
authors.forename: L A
authors.initials: LA
authors.lastname: Spacek
authors.forename: F
authors.initials: F
authors.lastname: Lutwama
authors.forename: H M
authors.initials: HM
authors.lastname: Shihab
authors.forename: J
authors.initials: J
authors.lastname: Summerton
authors.forename: M R
authors.initials: MR
authors.lastname: Kamya
authors.forename: A
authors.initials: A
authors.lastname: Ronald
authors.forename: O
authors.initials: O
authors.lastname: Laeyendecker
authors.forename: T C
authors.initials: TC
authors.lastname: Quinn
authors.forename: H
authors.initials: H
authors.lastname: Mayanja-Kizza
mesh_terms: D000328:Adult; D003906:Developing Countries; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D016655:HIV Core Protein p24 / Q000032:analysis*; D015658:HIV Infections / Q000097:blood / Q000175:diagnosis* / Q000276:immunology; D015497:HIV-1 / Q000302:isolation & purification; D006801:Humans; D016014:Linear Models; D011489:Protein Denaturation; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D012680:Sensitivity and Specificity; D014454:Uganda; D019562:Viral Load / Q000191:economics / Q000379:methods
chemical_list: D016655:HIV Core Protein p24