Measurement of plasma uroporphyrin during treatment and long-term follow-up of patients with Porphyria cutanea tarda.

.1 ml plasma was precipitated and extracted with 3 ml 0.61 mol/l trichloroacetic acid. After centrifugation the fluorescence intensity of the supernatant was measured using uroporphyrin as a standard. The porphyrins with a higher number of carboxylic groups (uroporphyrin and heptacarboxyporphyrin) were effectively extracted and the others, poorly or very poorly. Thus, the determined parameter was a mixture of chiefly highly carboxylated porphyrins. The results were expressed in nmol uroporphyrin/l. The coefficient of variation was 4%. No quenching of the fluorescence was established in higher plasma porphyrin concentrations. The range of the control group (n = 33) was 0-1.4 nmol/l. The data of the patients, needing treatment were within the interval of 17.9-448 nmol/l (n = 17). The correlation coefficient with the urinary uroporphyrin was 0.97. The values in the cases with remission (n = 74) ranged from 0 to 12.8 nmol/l. The method is particularly convenient for monitoring the effect of treatment in patients with Porphyria cutanea tarda, as well as for their long-term follow-up.