Here is a paraphrase of what my Functional Medicine Nurse had to say about it.
The old tests measure the nutrient levels in the blood serum. The nurse said that the blood is favored for nutrients. It steals nutrients from the cells, until the cells are depleted. The Spectra cell measures nutrients in white blood cells to determine if the cell is well nourished. It is believed that this is a better measure of the actual nutrients used by cells.
Last year my insurance company would not cover this test, because it was experimental. This year my insurance company does cover the test. The nurse said that Medicare now covers it, so the private companies follow suit.
I had a serum test in November and had a severe shortage of B vitamins, vitamin D, vitamin A and many others. I am now thinking that if my blood were that low, my cells had to be really sad. I had commented to my doctor that all of my tissues seemed irritated. However, I am happy to report that my Spectra Cell in June showed that my cells were now receiving adequate levels of almost every nutrient! I highly recommend the Spectra Cell test for help in determining how good your small intestine is absorbing nutrients, and your cells using them. Also to help decide which supplements need supplementing. I am feeling much better than last November. I am still recovering after 18 months gluten free. Yet, I have energy, a clear mind, and a drive to get things done.