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The value of confirmatory testing in early infant HIV diagnosis programmes in South Africa: A cost-effectiveness analysis.

The value of confirmatory testing in early infant HIV diagnosis programmes in South Africa: A cost-effectiveness analysis.
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Dunning L, Francke JA, Mallampati D, MacLean RL, Penazzato M, Hou T, Myer L, Abrams EJ, Walensky RP, Leroy V, Freedberg KA, Ciaranello A,


Dunning L, Francke JA, Mallampati D, MacLean RL, Penazzato M, Hou T, Myer L, Abrams EJ, Walensky RP, Leroy V, Freedberg KA, Ciaranello A, (click to view)

Dunning L, Francke JA, Mallampati D, MacLean RL, Penazzato M, Hou T, Myer L, Abrams EJ, Walensky RP, Leroy V, Freedberg KA, Ciaranello A,

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PLoS medicine 2017 11 2114(11) e1002446 doi 10.1371/journal.pmed.1002446

Abstract
BACKGROUND
The specificity of nucleic acid amplification tests (NAATs) used for early infant diagnosis (EID) of HIV infection is <100%, leading some HIV-uninfected infants to be incorrectly identified as HIV-infected. The World Health Organization recommends that infants undergo a second NAAT to confirm any positive test result, but implementation is limited. Our objective was to determine the impact and cost-effectiveness of confirmatory HIV testing for EID programmes in South Africa. METHOD AND FINDINGS
Using the Cost-effectiveness of Preventing AIDS Complications (CEPAC)-Pediatric model, we simulated EID testing at age 6 weeks for HIV-exposed infants without and with confirmatory testing. We assumed a NAAT cost of US$25, NAAT specificity of 99.6%, NAAT sensitivity of 100% for infants infected in pregnancy or at least 4 weeks prior to testing, and a mother-to-child transmission (MTCT) rate at 12 months of 4.9%; we simulated guideline-concordant rates of testing uptake, result return, and antiretroviral therapy (ART) initiation (100%). After diagnosis, infants were linked to and retained in care for 10 years (false-positive) or lifelong (true-positive). All parameters were varied widely in sensitivity analyses. Outcomes included number of infants with false-positive diagnoses linked to ART per 1,000 ART initiations, life expectancy (LE, in years) and per-person lifetime HIV-related healthcare costs. Both without and with confirmatory testing, LE was 26.2 years for HIV-infected infants and 61.4 years for all HIV-exposed infants; clinical outcomes for truly infected infants did not differ by strategy. Without confirmatory testing, 128/1,000 ART initiations were false-positive diagnoses; with confirmatory testing, 1/1,000 ART initiations were false-positive diagnoses. Because confirmatory testing averted costly HIV care and ART in truly HIV-uninfected infants, it was cost-saving: total cost US$1,790/infant tested, compared to US$1,830/infant tested without confirmatory testing. Confirmatory testing remained cost-saving unless NAAT cost exceeded US$400 or the HIV-uninfected status of infants incorrectly identified as infected was ascertained and ART stopped within 3 months of starting. Limitations include uncertainty in the data used in the model, which we examined with sensitivity and uncertainty analyses. We also excluded clinical harms to HIV-uninfected infants incorrectly treated with ART after false-positive diagnosis (e.g., medication toxicities); including these outcomes would further increase the value of confirmatory testing.

CONCLUSIONS
Without confirmatory testing, in settings with MTCT rates similar to that of South Africa, more than 10% of infants who initiate ART may reflect false-positive diagnoses. Confirmatory testing prevents inappropriate HIV diagnosis, is cost-saving, and should be adopted in all EID programmes.

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