Comparative study of two screening tests for urinary porphyrins in the diagnosis of porphyrias.

ABSTRACT

Objective: To evaluate the efficiency of two urinary porphyrins screening tests routine fluorescent detection and semi quantitative spectrophotometric scanning. Methods: Minimal-level detection was performed by adding standard coproporphyrin of 0, 25, 50, 100, 250 and 500 ตg/L in urine and then screened by the two methods. Urine samples from 39 controls, 7 patients with porphyrias and 20 patients with liver impairment were quantitated for total porphyrins, followed by a comparison of the two qualitative tests. Results: The fluorescent test detected the minimal porphyrin level at 250 ตg/L whereas spectrophotometric scanning could detect a lower level, at 100 ตg/L. Total control subjects showed negative results from both tests while all 7 patients with porphyrias and 6 out of 20 cases of liver impairment showed definite positive results. Conclusion: Urinary screening for porphyrins from both tests revealed the same accuracy from this study. Still, the spectrophotometric method which is simpler, more sensitive and easily interpretable seemed more practical as a screening test in general laboratories. Keywords Screening test; Porphyrias; Urinary porphyrins