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Resistance testing
Apr 17, 2000

If you have two blood work tests done (HIV RNA by PCR Quant & Total CD4 count) would the results of those two tests indicate if there is any resistance related to the virus you're carrying? Or does resistance testing need to be done separately? Is it expensive? Does it take long?

Response from Dr. Holodniy

The HIV RNA PCR test only measures how much virus is present in the blood. It does not tell us anything about the characteristics of the virus (ie resistance). That requires a special test. There are two kinds, genotypic testing, analyzes the sequence of the RNA looking for specific mutations that are known for drug resistance. Phenotypic testing measures the viruses ability to grow or not grow in the presence of HIV drugs. The former costs about $300-500 and takes about 1-2 weeks and the latter about $800-1,000 and takes about 2-4 weeks.


types of genotypic tests

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