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Confirmatory HIV testing prevents unnecessary treatment in infants
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The use of a second, confirmatory HIV test for infants in South Africa can reduce the number of false-positive results from 128 to 1 per 1,000 infants and is able to save costs related to unneeded treatment, according to a study published in PLOS Medicine.
“As the incidence of pediatric HIV falls with improved access to ART for pregnant and breast-feeding women, the positive predictive value of diagnostic assays also decreases, leading to a greater proportion of uninfected infants receiving false-positive diagnoses and starting ART,” Lorna Dunning, MBiochem, MPH, from the division of epidemiology and biostatistics in the School of Public Health & Family Medicine at the University of Cape Town, and colleagues wrote.
“After ART is initiated, it may be impossible to distinguish truly infected infants from uninfected infants because effective ART may lead to undetectable HIV RNA in HIV-infected infants whilst also preventing the development of endogenous anti-HIV antibody after maternal antibody fades from the circulation,” Dunning and colleagues continued. “Because truly infected infants may therefore have identical laboratory results to treated infected infants, they may face many years or even a lifetime of incorrect diagnosis and ART.”
To examine whether a second, confirmatory HIV test for children in early infancy demonstrates cost-efficacy and is impactful in preventing false diagnoses, the researchers conducted a simulation using the Cost-effectiveness of Preventing AIDS Complications-Pediatric model. The simulation included early infant diagnosis testing for infants aged 6 weeks who were exposed to HIV. Children who received confirmatory testing, and those who did not, were included.
Regarding nucleic acid amplification tests, Dunning and colleagues assumed each test would cost $25 (U.S.), with a specificity of 99.6%. For infants who were infected with HIV in utero or at least 4 weeks before testing was completed, the researchers assumed the test had a sensitivity of 100% and a mother-to-child transmission rate of 4.9% for those aged 12 months.
The researchers then simulated the rates of testing uptake, result return and ART initiation according to previously established guidelines. All infants were connected with care and treated over 10 years if they had false-positive results and for life if they had true positive results.
Of those included in the simulation with HIV, life expectancy remained the same whether or not confirmatory testing was completed (26.2 years). Those who were exposed to HIV had a life expectancy of 61.4 years. When confirmatory testing was not conducted, 128/1,000 infants who had false-positive results began ART. This number was significantly lower when confirmatory testing was completed (1/1,000).
The use of confirmatory testing was observed as cost-saving. The cost for a single infant with confirmatory testing equated to $1,790, whereas the cost without additional testing was equal to $1,830 per infant. The cost-efficacy did not change unless the infant underwent a nucleic acid amplification test that cost more than $400 or if a false-positive status was diagnosed, identified and ART was stopped within 3 months.
“False-positive results occur for a variety of reasons but are likely the result of stretched human resources compromising test specificity and sensitivity via specimen handling errors such as mislabeling of specimens, incorrect specimen placement in the device or inadequate quality control resulting in contamination between specimens during PCR amplification,” Dunning and colleagues wrote. “WHO recommends the use of a second specimen for a confirmatory test, ensuring the independence of the two assays and reducing the likelihood of a false-positive result.”
“Unconfirmed [early infant diagnosis] test results therefore cause diagnostic dilemmas for the provider, whilst families may experience confusion and uncertainty about the health system, discouraging future engagement in care,” Dunning and colleagues continued. – by Katherine Bortz
Disclosures: The authors report no relevant financial disclosures.
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