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Background:  The detection of HIV-1 by PCR is useful for the diagnosis of perinatal infection in infants. Commercially available PCR methods are based on elaborate amplification approaches, are expensive, and require skilled technicians with specialized equipment and facilities, making their use prohibitive for many resource-limited areas. An inexpensive and less complex approach for the diagnosis of HIV-1 infection in infants would be valuable in resource-limited settings. An inexpensive and more sensitive (as compared with standard p24) “boosted” p24 assay, combining heat denaturation and ELISA technology, has been previously described; however transfer of this approach has been limited by its research nature.

Methods:  A laboratory protocol, test kit, and software for an ultrasensitive p24 antigen assay (Up24) were developed based on the research version. To estimate the sensitivity and specificity of Up24 for use in infant HIV-1 diagnosis, 217 specimens from HIV-infected infants between 10 and 24 weeks of age from New York City and North Carolina, and 540 specimens from uninfected, HIV-exposed infants collected over a broad range of time-points (including 6 and 24 weeks) of age were tested by Up24. A subset of samples was also tested with a new extraction buffer reported to improve sensitivity. Results were compared to known infection status as determined by DNA PCR.

Results: Up24 with standard kit buffer was 94.0 % sensitive (95% confidence interval 90.0 to 96.8%), 98.7% specific (CI 97.4 to 99.5 %). Assuming an HIV prevalence of 28.7%, the Up24 assay yields a positive predictive value of 96.7% (CI 93.3 to 98.7 %) and negative predictive value of 97.6% (CI 96.0 to 98.7 %). Use of the new extraction buffer increased Up24 sensitivity to 96.7 % (CI 88.7 to 99.6 %) while specificity remained the same.

Conclusions:  Up24 may be useful as an inexpensive method to diagnose HIV-1 infection in infants applicable to resource-limited settings. Research is needed to determine at what age p24 antigen is reliably detected by Up24, and to evaluate the use of Up24 on infant specimens from settings where HIV-1 non-B subtypes predominate.

Keywords: Resource-limited; Diagnosis; Pediatrics