EVALUATION OF A FIRST-LINE SPECTROPHOTOMETRIC SCREENING-TEST FOR INCREASED URINE PORPHYRIN EXCRETION

We compared a spectrophotometric screening test for urine porphyrin co ncentration with a high performance liquid chromatography (HPLC) metho d. The screening test gave lower values than those obtained by HPLC, b ut the overall correlation was good. Occasionally, spectrophotometry f ailed to detect porphyrins in the urine which were detected by HPLC. T he type of porphyria had no influence on the efficacy of the screening method. Receiver operating characteristic plot analysis of the screen ing test led to a cut-off value of 110 nmol/24 h with a sensitivity of 96% and a specificity of 86%. We conclude that the spectrophotometric screening method is useful for detection of increased total urine por phyrin concentration.