• CD4s above 350, premeds
HIVspecialists mostly agree: STI success depends on your lowest-everpremeds CD4s—a.k.a your nadir—not your current labs. Boston HIV proPaul Sax, MD, says: “Folks whose CD4s have never been below 350 canlikely remain off therapy for months if not years.” Three studiesconclude that even HIVers with nadirs of 200 can take breaks ifcarefully monitored. But some supercautious docs suggest CD4s above 500(on meds) for a year pre-STI.

• CD4s below 350, premeds
YourSTI prospects are iffier. Cal Cohen, MD, director of Boston’s CommunityResearch Initiative of New England, which is conducting a multiyear STIstudy, says: “Some low-nadir people may have a rapid fall in CD4s. Butabout half will have at least six to eight months off before they needto restart.” Sax discourages those with nadirs below 350 from stoppingtherapy “unless there is bad med toxicity.” He says these folks “havethe greatest risk of high viral-load rebounds and rapid CD4 drops whenthey stop.” But Cohen says, “On effective combos, you can regrow CD4sregardless of the starting CD4 level.”

• Travel Advisory: Treatment Failure
Threerecent studies rule out STIs between ending a combo that has  bredmucho drug resistance and starting a new one. In this case, the STI maycause viral-load rebounds and big CD4 drops—and perhaps other healthproblems. One study found that HIVers who had tried several comboswithout reaching undetectable did poorly on STIs.