a negative or positive test for many things does not rule out (or in) the condition. for example my neuro scores on nerve conduction were positive for tos but the test where you are raising the arm up was negative.

i had negative tests for carpal tunnel but was still diagnosed with it.

my thyroid blood tests are normal yet i have a nodule.

i suspect much of medicine is in its infancy. the good doctors can only do the best they can.