title: Adaptation of the ultrasensitive HIV-1 p24 antigen assay to dried blood spot testing.
abstract: Implementation of molecular tests for the assessment of pediatric HIV-1 infection in resource-limited countries is difficult because of technical complexity and costs. Alternatives like the ultrasensitive HIV-1 p24 antigen enzyme-linked immunosorbent assay have therefore been proposed. We have now adapted this test to dried blood spot (DBS) plasma p24 antigen (p24). High background activity was recognized as originating from endogenous peroxidase and eliminated by H2O2 quenching. The assay was evaluated with 72 pediatric specimens from Tanzania and with 210 pediatric or adult specimens from Switzerland. A real-time polymerase chain reaction assay for DBS DNA and/or plasma RNA identified HIV-1 infection in 38 Tanzanian children. HIV-1 subtypes included 18 C, 9 A1, 8 D, 1 AC, 1 J-like, and 1 unidentified. The detection rates for the different assays were as follows: DBS-p24, 32 (84%) of 38 samples; DBS DNA, 30 (79%) of 38 samples; plasma-p24, 23 (85%) of 27 samples; and plasma RNA, 30 (100%) of 30 samples. False-negative DBS-p24 was associated with subtype D (P < 0.01). DBS-p24 detection for non-D subtypes was 93% (95% confidence interval: 81% to 99%), and for subtype C, it was 94% (95% confidence interval: 76% to 99%). Specificity among 193 HIV-negative DBS samples was 100%. Correlation of DBS-p24 and plasma-p24 concentrations was excellent (R = 0.83, P < 0.0001). DBS-p24 is thus a promising alternative to molecular tests for HIV-1 in subtype C regions. It should now be evaluated in large studies of children for accurate assessment of diagnostic sensitivity.
authors.affiliation: Swiss National Centre for Retroviruses, University of Zürich, Gloriastrasse 30/32, CH-8006 Zürich, Switzerland.
authors.forename: Marlyse C
authors.initials: MC
authors.lastname: Knuchel
authors.forename: Boniphace
authors.initials: B
authors.lastname: Jullu
authors.forename: Cyril
authors.initials: C
authors.lastname: Shah
authors.forename: Zuzana
authors.initials: Z
authors.lastname: Tomasik
authors.forename: Marcel P
authors.initials: MP
authors.lastname: Stoeckle
authors.forename: Roberto F
authors.initials: RF
authors.lastname: Speck
authors.forename: David
authors.initials: D
authors.lastname: Nadal
authors.forename: Hassan
authors.initials: H
authors.lastname: Mshinda
authors.forename: Jürg
authors.initials: J
authors.lastname: Böni
authors.forename: Marcel
authors.initials: M
authors.lastname: Tanner
authors.forename: Jörg
authors.initials: J
authors.lastname: Schüpbach
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D004279:DNA, Viral / Q000097:blood; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods*; D005188:False Negative Reactions; D016655:HIV Core Protein p24 / Q000097:blood*; D015658:HIV Infections / Q000175:diagnosis*; D015497:HIV-1 / Q000145:classification / Q000276:immunology / Q000302:isolation & purification*; D006801:Humans; D007223:Infant; D012367:RNA, Viral / Q000097:blood; D012680:Sensitivity and Specificity; D013557:Switzerland; D013636:Tanzania
chemical_list: D004279:DNA, Viral; D016655:HIV Core Protein p24; D012367:RNA, Viral