Study Finds PhenoSense Assay More Precise Than the Antivirogram Assay and Superior at Detecting Resistance to Abacavir, Didanosine and Stavudine

The PhenoSense and the Antivirogram assays are widely used resistance assays, but prior to the current study, no one had yet evaluated their sensitivity and precision. To assess the precision of the Antivirogram and PhenoSense assays, researchers examined susceptibility results of HIV-1 isolates lacking drug resistance mutations and containing matching patterns of drug resistance mutations.

To assess sensitivity, they determined for each assay the proportion of isolates with common patterns of matching drug resistance mutations having reductions in susceptibility greater than those in isolates without drug resistance mutations.

Results

The investigators analyzed protease inhibitor (PI) susceptibility results obtained by the Antivirogram assay for 293 isolates and by the PhenoSense assay for 300 isolates.

They  analyzed reverse transcriptase (RT) inhibitor susceptibility results obtained by the Antivirogram assay for 202 isolates and by the PhenoSense assay for 126 isolates.

For wild-type and mutant isolates, the median absolute deviance of the fold resistance of nucleoside RT inhibitor susceptibility results was significantly lower for the PhenoSense assay than for the Antivirogram assay.

The PhenoSense assay was also significantly more likely than the Antivirogram assay to detect resistance to abacavir (Ziagen), didanosine (Videx), and stavudine (Zerit) in isolates with the common drug resistance mutations M41L, M184V, and T215Y (+/-L210W).

They found no significant differences between the 2 assays for detecting PI and non nucleoside RT inhibitor resistance.

The authors conclude, “The PhenoSense assay is more precise than the Antivirogram assay and superior at detecting resistance to abacavir, didanosine, and stavudine.”

03/28/05

Reference
J Zhang and others. Comparison of the Precision and Sensitivity of the Antivirogram and PhenoSense HIV Drug Susceptibility Assays. Journal of Acquired Immune Deficiency Syndromes 38(4): 439-444, April 1, 2005.

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