Someone please tell me just what the $%#*@ these labcoat-type terms mean
CD4 percentage. Everybody knows that CD4 cells are the body’s elite HIV shock troops. But doctors also track your CD4 percentage—the fraction of CD4s that make up your lymphocytes, the commanders of your immune system. See, your CD4 count routinely bobs up and down, but your CD4 percentage varies far less from one lab test to the next— making it a reliable long-term marker of immune health. So if your CD4 count dropped from 400 on one lab to 200 on the next, it might be because your lymphocytes dropped from 1,000 to 500. On both labs, your CD4 percentage is still 40 percent. And since docs consider a percentage of 20 or above safe ground, don’t panic—but do follow the trend over time.
Log change. This term for tracking viral load is so simple, Paul Bunyan would understand. A one-log change in viral load either adds or drops a zero (or a factor of 10), a two-log change adds or drops two zeroes, etc. So a one-log viral-load drop from 100,000 equals 10,000, and a three-log drop equals 100—nearly undetectable! Docs will usually raise an eyebrow only if viral load changes by a “power of three” or more (say, from 90K to 30K or lower)—so three successive readings of 20K, 30K and 40K wouldn’t be a too-scary surge.