AEGiS-14IAC: Evaluation of an ultrasensitive p24 antigen assay (UPTA) as a possible surrogate marker of HIV-1 RNA in resource-poor settings.

14th International AIDS Conference

Barcelona, Spain - July 7-12, 2002

Evaluation of an ultrasensitive p24 antigen assay (UPTA) as a possible surrogate marker of HIV-1 RNA in resource-poor settings.

Int Conf AIDS 2002 Jul 7-12; 14:(abstract no. WeOrB1341)

Respess R, Cachafeiro A, Withum D, Fiscus S, Newman D, Cabruja I, Branson B, Varnier O, Dondero T
Centers for Disease Control and Prevention, Atlanta, GA, United States

BACKGROUND: The measurement of RNA viral load (VL) is useful for the clinical management of HIV infection. Commercially available VL quantitation methods are based on expensive nucleic acid-based amplification approaches requiring skilled technicians, specialized equipment, and dedicated facilities, making their use prohibitive for many resource-poor settings. A simple, sensitive, yet inexpensive HIV-1 quantitation based on modifications of a commercially available p24 antigen assay has been previously described, but has met with limited success in transferability of laboratory methods.

METHODS: To address this, a laboratory protocol, integrated test kit, and dedicated reader software were developed and evaluated based on the modified p24 antigen assay. Anonymized sera from 39 newly diagnosed persons with HIV-1 subtype B were blinded, tested in duplicate by UPTA, and compared with previously determined VL. Log 10 transformation of VL and the average of duplicate UPTA test results were compared by Pearson product-moment correlation coefficient to assess strength of statistical relationship.

RESULTS: UPTA and VL test results were highly correlated overall (r = 0.87 [p < .001], r2 = 0.76). Correlation of UPTA and VL on specimens with VL < 5,000 (r = 0.94 [p < 0.0001], r2 = 0.88) and with VL > 5,000 (where higher values were truncated), (r = 0.64 [p < 0.001], r2 = 0.41) was significant in both groups. Correlation of duplicate testing of same sample was high (r = 0.89 [p < 0.0001]).

CONCLUSIONS: The UPTA and VL results were highly correlated indicating that UPTA may be a suitable surrogate for VL on HIV-1 subtype B specimens. UPTA may be potentially useful as a simple, and less expensive approach to VL in clinical staging, treatment monitoring, and pediatric diagnoses in resource-poor settings. Studies to assess assay in sequential sera from persons on treatment, and in non-B subtypes, are ongoing.

Keywords: AEGIS, Viral Load, HIV-1, Evaluation Studies, HIV Infections, Biological Markers, Health Resources, Laboratory Techniques and Procedures, CD4 Lymphocyte Count, AIDS Serodiagnosis, Enzyme-Linked Immunosorbent Assay, Child

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