Porphobilinogen low...Porphyria?

Hi, I have a low porphobilinogen test after the Zhang protocol and Wahls diet to treat CPN(Chronic Fatigue Syndrome)) for 2 months. Awful symptoms led me to have this test done. Is this porphyria? 

Porphobilinogen concentration was below sensitivity of the assay, 0.5 mg/L. Therefore the result was <1.1 mg/g creatinine. This result was calculated by dividing 0.5 mg/L by the creatinine concentration in g/L

Interpretation: Porphobilinogen (PBG was below the normal range). The clinical significance of decreased PBG is uncertain. However, it has been found in a few cases of aminolevulinic acid dehydratase deficiency porphyria (ADP)

These results have been flagged as falling outside of reference interval, which are not mentioned in the interpretation.

TomF - 50 yrs old, diagnosed CFS Jan.2000, CPN IGA 1:32 IGG 1:128 feb 2017

I have had another test done 10 days later with the same result. My doctor says hes not smart enough to know what this means and does nothing. Does anyone have any possibilities what low Porphobilinogens could mean? 

TomF - 50 yrs old, diagnosed CFS ;Jan 2000 - Nerve Conduction test shows moderate neuropathy in legs CPN IGA 1:32 IGG 1:128 feb 2017 CPN Retested after 3 month CAP protocol CPN IGA >1:16 IGG 1:128 - symptoms persist