COMPARISON OF THE BIO-RAD PORPHYRIN COLUMN TEST WITH A SIMPLE SPECTROPHOTOMETRIC TEST FOR TOTAL URINE PORPHYRIN CONCENTRATION

We compared two screening methods for increased urine porphyrin concen tration and compared the results with a high-performance liquid chroma tography (HPLC) method. The screening methods were the Bio-Rad (Porphy rin) Column Test and a simple spectrophotometric method. Results were obtained for urines with three different porphyrin patterns. Both scre ening methods were easy to perform. The accuracy and precision of the spectrophotometric method were both slightly better than that of the B io-Rad Column Test. Recovery measurements in samples with different po rphyrin patterns varied between 73% and 59% (n=12) for the spectrophot ometric method and between 82% and 116% (n = 12) for the Bio-Rad Colum n Test as compared to HPLC. Between batch precision measurements revea led coefficients of variation for spectrophotometric and Bio-Rad metho ds for 2%-4% and 4%-10%, respectively. The recovery of the porphyrins illustrates the Bio-Rad Column Test to be more susceptible to variatio n in urine porphyrin composition. Both methods will show satisfactory results in cases of overt porphyria because of the high urine porphyri n concentration.