Dx'ng is a process of evaluation with 99.9% of the tests showing negative.
Everything's OK.
That's why he Dx is subjective, assessing many factors,
and eventually coming up with idiopathic much of the time.
Its a long process (and an expensive one) because the causes of PN are elusive,
but the symptoms are not elusive, only the over 200 known causes
and which to use of over 75 different meds to treat it.