Rapid procedure for fecal porphyrin assay

Hydrochloric acid extraction of feces in the presence of ether yields an extract suitable for spectrophotometric estimation of total porphyrin and for further separation by "high-performance" liquid chromatography (HPLC) or thin-layer chromatography. A total porphyrin reference interval of less than 200 nmol/g dry weight of feces was established from data on 106 normal subjects on an unrestricted diet. Total fecal porphyrin values in 11 porphyria cutanea tarda patients were considerably higher than given by the widely used Rimington method (respective means, 652 and 239 nmol/g dry weight). Our HPLC method for separation of porphyrin methyl esters on a silica column, with quantification by fluorescence, is described. HPLC separations performed on 23 porphyria cutanea tarda patients gave the following mean proportions of total fecal porphyrins: dicarboxylics 21%, coproporphyrin 9%, isocoproporphyrins 28%, pentacarboxylporphyrin 9%, hexacarboxylporphyrin 11%, heptacarboxylporphyrin 18%, and uroporphyrin 4%.