Dear Dr. I have been taking D4T and 3TC for about two years and recently had my blood drawn for my 3 month count evaluation my CD4 count dropped a little and my viral load went up 4 fold, from 4,000 to 16,000. My doctor suggested this new test called Phenosense, if I am spelling that correctly, which supposedly determines which medicines one is resistant to and which ones they are not. My result from the test indicated that I am highly resistant to the 3tC and also AZT and Abacavir. So now I am faced switching to a new drug regimen. What would your recommendation be for me at this point? Respectfully, Man from Seattle

A man from my home town. The PhenoSense assay measures the ability of your virus to grow in the presence of HIV drugs. Based on what you are on, the 3TC resistance is easy to explain. d4T can produce what has been called in the past "AZT-associated mutations". Since d4T and AZT are close cousins chemically, it makes some sense that these mutations could be produced by both. So d4T can create AZT resistance. When you have AZT and 3TC resistance, you can also get abacavir resistance. If those are the only 2 drugs you have been on, you have lots of options. MH