I've done some research on this test. The FDA analyzed the original study of the test, and found that it was not conducted in an accurate manner. Here's what the FDA's report says:
"A small 2012 study (110 fibromyalgia patients, 91 controls) reported a lower-than-normal cytokine immune response among patients with fibromyalgia compared to controls. The FM/a Test appeared on the market within months of this publication, offered as an LDT claiming to diagnose the disease by documenting altered immunity as an explanation of symptoms experienced by fibromyalgia patients. The manufacturer suggests that the test diagnoses the disease, and markets the test for people undergoing a diagnostic workup of fibromyalgia.
A number of critiques of the study methodology appeared subsequently. These included concerns that the control group was inadequate and that the authors had not adjusted for other conditions known to change cytokine levels that may have been present at different rates in the fibromyalgia and control groups. The company failed to conduct clinical trials to verify that the immune system deficiency reported in the study was clinically relevant to fibromyalgia. Approximately 1,000 tests were sold for $744 apiece during the first month the test was offered.
Making an inaccurate diagnosis of fibromyalgia can be especially harmful when the patient may be suffering from a different, treatable condition with similar symptoms. Such conditions include Lyme disease and rheumatoid arthritis, for which effective therapies exist. Moreover, patients wrongly diagnosed with fibromyalgia may take unnecessary medications for that condition and be exposed to associated adverse effects."
I also know, because of the low accuracy rate, that most insurance companies won't cover the test, which is quite expensive.