September 26, 2005
Resistance to antiretroviral therapy, even in patients who have never received treatment, is a growing concern. However, genotype resistance testing, which involves looking for the presence of resistance genes, is not a standard procedure at the time a patient is diagnosed with HIV, probably due to lack of data on its benefits and its relatively high cost compared with other routine blood tests.
A cost-effectiveness analysis conducted by a group of Boston researchers indicates that performing genotype resistance testing at initial HIV diagnosis -- before treatment is started -- can effectively guide a physician's choice of treatment regimen and increase a patient's quality-adjusted life expectancy. (Quality-adjusted measurements of time reflect that survival with an illness is presumed to be of lower quality than healthy survival.)
"For the approximately 90 percent of patients with no resistance, the testing provides no benefit," said lead author Paul Sax, M.D., of Brigham and Women's Hospital. "However, if certain types of resistance are present [when a patient is first diagnosed with HIV], our study projects a substantial increase in survival" of more than 14 months, compared with no resistance testing.
Resistance rates vary from place to place. It is estimated that, in the United States and Europe, the average resistance rate in treatment-naive patients is between 8 and 10 percent, although baseline resistance may be as high as 16 percent in gay men, "likely reflecting their overall greater access to treatment since the beginning of the epidemic," said Dr. Sax. Using a model with a resistance rate of just over 8 percent, the analysis estimated a cost of $23,900 per quality-adjusted life year gained, which is within the range of other commonly accepted HIV interventions. The cost-effectiveness calculation remained below $50,000 per quality-adjusted year gained unless the resistance rate was 1 percent or less, which is much lower than in most areas.
An accompanying editorial commentary by Frederick Hecht, M.D., and Robert Grant, M.D., of the University of California, San Francisco, agrees that "there is now sufficiently strong information to recommend genotypic resistance testing in all drug naive patients at the time of diagnosis." However, the authors, who have received support from various pharmaceutical and diagnostic companies, caution that there are some drug resistance mutations that may not be detectable by standard resistance tests.
The cost of performing the one-time test -- now about $400 -- has decreased from when it was first approved, and will likely continue to drop. Some physicians are not yet convinced of the value of genotype resistance testing, and some insurance companies do not yet cover it, but the practice of resistance testing at initial HIV diagnosis has gradually increased. "We're hoping that this study makes it part of standard care," said Dr. Sax.