3-Carboxy-4-methyl-5-propyl-2-furanpropionsäure als mögliche Ursache für falsch niedrig bestimmte Albuminwerte im Serum mittels der Bromkresolpurpurmethode bei Hämodialysepatienten

The aim of this study was to examine the applicability of the new dye-binding method BCP for haemodialysis patients and to investigate the influence of CMPF dye-binding methods. Albumin was determined in a group of HD patients (n=124) and a group of non-HD patients (n=101) by the dye-binding methods BCG and BCP and an immunological reference method. The results from the different methods within the two groups were compared with each other. The CMPF quantitation was done in accordance to a published method that was optimized for this study. The influence of other substances with high albumin binding affinity was also investigated by adding ascending concentrations of the drug of interest to plasma froma fasting proband with no medication. The albumin was then measured by the two dye-binding methods BCG and BCP and a nephelometric method. The albumin measurements by the new BCP method showed – in comparison to the BCG method – a wrong negative deviation for the albumin values up to 39,7% in the group of haemodialysis patients. The negative deviation was highest in hypoalbuminaemic samples and decreased proportionality with increased albumin concentrations. In the group of non-HD patients there was no wrong negative deviation for the albumin values by the BCP method in comparison to the BCG method. Especially in hypoalbuminaemic samples, an overestimation of albumin values was attested. The new BCP method showed in comparison to the immunological method an underestimation of albumin values in both groups. The albumin measurements by the BCG method showed – in comparison to the immunological method – an overstimation of albumin values in both groups, which was especially marked in hypoalbuminaemic samples. In a test series with CMPF-spiked plasma samples a wrong negative deviation of albumin values with increasing CMPF concentrations for the BCP method was observed, but it was not observed for the BCG method. This effect was most marked in hypoalbuminaemic samples. The quantitation of CMPF showed marked higher concentration of CMPF in average in the group of haemodialysis patients in comparison to the control group. Optimizing the originally published method for the quantitation of CMPF lead to a significant less sample volume of 100 µl and shorter analysis time. We succeded in inserting marked lower volumes now. The results of the method validation with intra-assay CVs between 4.3 % and 12.8 % throughout the entire measuring range and coefficients of correlation R2 between 0.9717 and 0.9990 for all of the calibration curves were satisfactorily. Even though our study showed no significant correlation between the plasma CMPF concentration and the deviation of albumin values by the BCP method, the test series with CMPF-spiked samples showed an increasing negative influence on the BCP albumin determination with increasing CMPF concentrations. Other drugs with high albumin binding affinity could be excluded as far as tested. Despite high financial costs, the immunological methods being the most reliable methods should be used for such a crucial laboratory value as albumin in therapy and running assessment of chronic renal insufficiency and haemodialysis. The CMPF concentration could be included in the decision making across the choice of suitable albumin determination methods for haemodialysis patients. In future studies there should be further research into the interactions between uremic toxins and other retention substances by the dye-binding methods to achieve a standardization in the albumin determination in case of haemodialysis patients.