I have just come across the buspirone challenge test, a straightforward blood test for ME/CFS which measures how much of the hormone prolactin is released into the bloodstream when a single dose of the drug buspirone is given orally (buspirone is an anti-anxiety drug). I was so intrigued by this test (which I had not heard of before), that I put together a new MEpedia article detailing the buspirone challenge method of detecting ME/CFS. As the article explains, ME/CFS patients release substantially more prolactin into their bloodstream when given buspirone, compared to healthy controls AND compared to depressed patients. So this test seems to reliably detect ME/CFS, and can clearly distinguish ME/CFS from depression. The test involves giving patients a single oral dose of buspirone, typically around 35 to 60 mg, and measuring the prolactin levels in the blood just before giving this drug, and again an hour after administration of the the drug. Everyone will release more prolactin into the blood when stimulated by buspirone, but you can see from the graphs in the article how ME/CFS patients release a lot more prolactin than healthy people. In one study, mean buspirone-stimulated prolactin levels in ME/CFS patients were 3 times higher than those of controls. Buspirone activates the serotonin receptors in the hypothalamus (specifically the 5-HT1A receptors), and one theory posits that the serotonin receptors in the hypothalamus are more sensitive in ME/CFS patients, which is why it is believed buspirone stimulates the release of higher amounts of prolactin in ME/CFS patients compared to healthy people. Though this theory is contested. The studies found ME/CFS patients often feel some lightheadedness and nausea when given buspirone, whereas healthy controls tend not to get these symptoms. So a lightheadedness and nausea response to an oral dose of buspirone is also to some extent diagnostic for ME/CFS. I remember years ago when I tried buspirone to treat my generalized anxiety disorder, I became lightheaded and slightly dizzy literally within 20 minutes of taking a 10 mg buspirone tablet. At that time, I just thought this was a side effect of the drug, but now I realize the side effects I experienced actually help confirm my ME/CFS. But the question I would like to ask is why isn't this testing being validated and deployed for clinical use? As we know, ME/CFS is considered a wastebasket diagnosis, and thus you will have people with other diseases misdiagnosed with ME/CFS. A simple and cheap test such as this could be very useful in clinical settings to verify an ME/CFS diagnosis. There is a slight issue with using the buspirone challenge test on women, which is that you get variations in prolactin release depending upon the phase of menstruation; but one study found that provided you administer the test during the luteal phase, you get consistent results. With males, the test can be administered at any time.