Comparison of the Bio-Rad Porphyrin Column Test with a Simple Spectrophotometric Test for Total Urine Porphyrin Concentration

Abstract

We compared two screening methods for increased urine porphyrin concentration and compared the results with a high-performance liquid chromatography (HPLC) method. The screening methods were the Bio-Rad (Porphyrin) Column Test and a simple spectrophotometric method. Results were obtained for urines with three different porphyrin patterns. Both screening methods were easy to perform. The accuracy and precision of the spectrophotometric method were both slightly better than that of the Bio-Rad Column Test. Recovery measurements in samples with different porphyrin patterns varied between 73% and 59% (n = 12) for the spectrophotometric method and between 82% and 116% (n = 12) for the Bio-Rad Column Test as compared to HPLC. Between batch precision measurements revealed coefficients of variation for spectrophotometric and Bio-Rad methods for 2%-4% and 4%-10%, respectively. The recovery of the porphyrins illustrates the Bio-Rad Column Test to be more susceptible to variation in urine porphyria composition. Both methods will show satisfactory results in cases of overt porphyria because of the high urine porphyrin concentration.