Urinary total porphyrins by ion exchange analysis: reference values for the normal range and remarks on preformed prophyrins in acute porphyria urine.

Determination of total porphyrin with a rapid and east method (ion exchange; spectrophotometry) was performed on 57 morning urine samples from laboratory personnel, 59 arbitrary day urine samples from blood donors, and 90 24-hour urines from medical inpatients. The upper reference limit for morning urine was 0.32 mumol/l but even a value as high as 0.7 mumol/l was found. In the donor urines the upper limit was 0.155 mumol/l. The 24-hour urines showed an upper reference limit of 271 microgram/24 h. These values are in good agreement with values from the literature, mostly based on extraction analyses. Tracings of the absorption curves in the region of 380--430 nm were performed in all analyses and showed that the non-porphyrin absorption was close to linear in most cases. Studies of porphyric urines gave no support to the claim that preformed porphyrins not formed from porphobilinogen are excreted in this disease.