Antiretroviral treatment monitoring with an improved HIV‐1 p24 antigen test: an inexpensive alternative to tests for viral RNA

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Abstract
Monitoring of viral RNA has become indispensable for the management of HIV‐1 infection, but is expensive. This study investigated whether a highly improved test for p24 antigen could serve as an alternative. Thirty‐four patients enrolled during 1997 into two treatment studies were tested prospectively for viral RNA by the Roche HIV‐1 Monitor® and for p24 antigen using signal‐amplification–boosted ELISA of heat‐denatured plasma. P24 antigen was detectable in 75.8% of 178 samples and HIV RNA in 73.9% of 138 samples. The half‐life of p24 antigen in the first phase of effective treatment was 1.6 ± .4 days (RNA, 1.7 ± .8). An apparent second, slower decay phase had a half‐life of 42 ± 16 days. Treatment failure occurred in 14 patients. Secondary treatment failures with RNA rebounds from undetectable levels to ≤ 103 copies/ml in two patients with an undetectable viral load and 103 HIV RNA copies/ml, respectively, at baseline were not detected by p24 antigen but carried a low risk for secondary resistance mutations. The other 12 failures were on average detected 29 days earlier by p24 antigen than by RNA (P = .0204), owing to slightly more frequent testing for p24 than for RNA (2.7 vs. 2.4 tests). Average costs for p24 antigen testing up to a failure were only 20.5% of those for RNA (P < .0001). These results indicate that heat‐denatured, amplification‐boosted p24 antigen measurement can be used as a simple and inexpensive alternative to HIV RNA testing for monitoring treatment. J. Med. Virol. 65:225–232, 2001.
Funding Information
  • Swiss Federal Office of Public Health