New technique for diagnosis and monitoring of alcaptonuria: quantificationof homogentisic acid in urine with mid-infrared spectrometry

For the first time we used Fourier transform-infra-red (FT-IR) spectrometry in the investigation of an inborn error of metabolism, i.e. alcaptonuria, which expresses itself by the excretion of high concentrations of homogenti sic acid in urine. The 200 homogentisic acid-spiked urine samples, ranging from 0 to 60 mmol l(-1), were analysed in the mid-IR region using an attenu ated total reflection accessory. Quantification is performed with partial l east squares regression analysis. The standard errors of calibration, cross validation and prediction in the IR-predicted homogentisic acid concentrat ion are 0.64, 0.78 and 0.79 mmol l(-1),respectively, with R-2 > 0.998. The 2 sigma detection limit is 2.0 mmol l(-1) and the intra- and inter-assay co efficients of variation are below 5% for three concentration levels. The cl ear difference in the concentrations of homogentisic acid in the urine of f our alcaptonuria patients compared to seven control samples demonstrates th e potential suitability of IR analysis for the diagnosis and monitoring of alcaptonuria patients. (C) 2001 Elsevier Science B.V. All rights reserved.