Neurotransmitters are difficult, and testing things inside of the blood brain barrier (BBB) is notoriously difficult. While we can conduct blood tests of all three of those molecules, serum levels (that's what we call the blood after the red blood cells have been separated from the rest of the blood) do not correlate to levels on the other side of the BBB. That being said, the method for testing it would be either spectrophotometry or liquid chromatography mass spectroscopy (LCMS) depending on the medical facility and it's equipment/age.