Albumin as an outcome measure in haemodialysis in patients: the effect of variation in assay method.
BACKGROUND: Serum/plasma albumin is an important predictor of future mortality/morbidity in haemodialysis (HD) patients and has been proposed as an important audit measure. Different methods of albumin assay give different results and the bias between methods may be greater in renal failure patients. METHODS: Albumin concentration in plasma was measured by three methods, two dye-binding methods (bromocresol green (BCG) and bromocresol purple (BCP)) and an immuno-turbidimetric (ITM) method, in 143 HD patients (group I) and 49 non-renal patients (group II). Comparisons were made between means, variation in differences across a range of albumin concentrations and on the percentage of patients within the normal range. RESULTS: In HD patients (group I), BCG over-estimated plasma albumin compared with the other two methods. The difference could be as much as 10 g/l and was more marked in hypoalbuminaemic patients. The BCP method gave results closer to the ITM method, particularly in HD patients. These differences were less marked in group II patients but both methods overestimated albumin compared with the ITM method. Using the BCG local laboratory normal range, 84% of HD patients had plasma albumin concentrations within the normal range but this fell to 57% if the BCP results were used. CONCLUSIONS: The method for determining albumin concentration has a marked effect on the results particularly in HD patients. BCG, the most commonly used method, gives higher results than other methods and correlates poorly with an immunological method. These differences make comparative audit between nephrology units difficult and have implications for other biochemical variables and other specialties. (+info)
Conversion between bromcresol green- and bromcresol purple-measured albumin in renal disease.
BACKGROUND: Albumin measured by a bromcresol purple dye-binding assay (Alb(BCP)) agrees more closely with the gold standard of immunonephelometry than does bromcresol green (Alb(BCG)) measurement. Both tests are in current clinical use. A method for converting between the two would be useful. METHODS: We measured albumin by bromcresol green and bromcresol purple in 535 patients, 155 of whom had renal disease. We randomly divided data from the patients with renal disease into two equal-sized sets, and used one set to derive, and the remaining set to validate, a regression equation relating the two values. RESULTS: The relationship Alb(BCG)=5.5+Alb(BCP) performed very well in both the renal patient validation set and in the data from 380 unselected in-patients and out-patients. Intraclass correlations for agreement between measured Alb(BCG) and predicted Alb(BCG) was 0.98 in both analyses. CONCLUSIONS: The ability to convert between these measurements will be of use in clinical situations where the absolute value of the serum albumin is important, when data from laboratories using different methodologies must be combined, and in the application of the Modification of Diet in Renal Disease formula to estimate glomerular filtration rate in patients whose albumin has been measured by bromcresol purple. (+info)
Guidance for selecting the measurement conditions in the dye-binding method for determining serum protein: theoretical analysis based on the chemical equilibrium of protein error.
A methodology for selecting the measurement conditions in the dye-binding method for determining serum protein has been studied by a theoretical calculation. This calculation was based on the fact that a protein error occurs because of a reaction between the side chains of a positively charged amino acid residue in a protein molecule and a dissociated dye anion. The calculated characteristics of this method are summarized as follows: (1) Although the reaction between the dye and the protein occurs up to about pH 12, a change in the color shade, called protein error, is observed only in a pH region restricted within narrow limits. (2) Although the apparent absorbance (the absorbance of the test solution measured against a reagent blank) is lower than the true absorbance indicated by the formed dye-protein complex, the apparent absorbance correlates with the true absorbance with a correlation coefficient of 1.0. (3) At a higher dye concentration, the calibration curve is more linear at a higher pH than at a lower pH. Most of these characteristics were similarly observed experimentally in the reactions of BPB, BCG and BCP with human and bovine albumins. It is concluded that in order to ensure the linearity of the calibration curve, the measurement should be performed at a higher dye concentration and sufficiently high pH where the detection sensitivity is satisfied. (+info)
Correlation of the suicide phenomenon in Aeromonas species with virulence and enteropathogenicity.
Certain strains of mesophilic Aeromonads like A. hydrophila, A. veronii biotype sobria and A. caviae when grown in broth containing 0.5% glucose, undergo growth inhibition concomitant with acetate accumulation. As these strains become nonviable after 24 h, this phenomenon is termed suicide. We investigated suicidal strains of Aeromonas species as means of understanding animal virulence and enteropathogenicity. Non suicidal strains of A. Hydrophila showed and overall 88.8% lethality rate and non suicidal strains of A. veronii biotype sobria showed 83.3% lethality rate and was nil for its suicidal part. Of the two suicidal A. caviae strains tested, none were lethal. The present data suggest that the suicide phenomenon may explain strain specific [A. veronii biotype sobria, A. hydrophila] and species specific [A. caviae] virulence and enteropathogenicity. (+info)
Measurement of serum albumin by capillary zone electrophoresis, bromocresol green, bromocresol purple, and immunoassay methods.
BACKGROUND/AIMS: The introduction of capillary zone electrophoresis (CZE) to this laboratory has highlighted discrepancies in albumin measured on an Abbott Aeroset by bromocresol green (BCG) and that calculated by CZE on the basis of total protein measured by Biuret. METHODS: This study examined differences in albumin estimation by CZE, Abbott Aeroset BCG, and Aeroset bromocresol purple (BCP), and compared these with albumin estimated by Beckman Array immunoassay. RESULTS: Altman and Bland analysis of results showed a positive bias of BCG with CZE (4.51 g/litre; 95% limits of agreement, 3.77 to 5.26; n = 72) and BCP (3.85 g/litre; 95% limits of agreement, -1.42 to 9.12; n = 72). CZE and BCP agreed closely (0.67 g/litre; 95% limits of agreement, -4.39 to 3.06; n = 72). Analysis of 57 of those samples in which BCG and CZE differed > or = 5 g/litre showed a positive bias of BCG with immunoassay (8.35 g/litre; 95% limits of agreement, 1.54 to 15.16; n =57), with good agreement between CZE and immunoassay (-0.44 g/litre; 95% limits of agreement, -2.82 to 1.94; n = 57). CONCLUSIONS: BCP is superior to BCG for the assay of albumin and has replaced BCG as the routine test for albumin in this laboratory. (+info)
Identification of the human mitochondrial S-adenosylmethionine transporter: bacterial expression, reconstitution, functional characterization and tissue distribution.
The mitochondrial carriers are a family of transport proteins that, with a few exceptions, are found in the inner membranes of mitochondria. They shuttle metabolites and cofactors through this membrane, and connect cytoplasmic functions with others in the matrix. SAM (S-adenosylmethionine) has to be transported into the mitochondria where it is converted into S-adenosylhomocysteine in methylation reactions of DNA, RNA and proteins. The transport of SAM has been investigated in rat liver mitochondria, but no protein has ever been associated with this activity. By using information derived from the phylogenetically distant yeast mitochondrial carrier for SAM and from related human expressed sequence tags, a human cDNA sequence was completed. This sequence was overexpressed in bacteria, and its product was purified, reconstituted into phospholipid vesicles and identified from its transport properties as the human mitochondrial SAM carrier (SAMC). Unlike the yeast orthologue, SAMC catalysed virtually only countertransport, exhibited a higher transport affinity for SAM and was strongly inhibited by tannic acid and Bromocresol Purple. SAMC was found to be expressed in all human tissues examined and was localized to the mitochondria. The physiological role of SAMC is probably to exchange cytosolic SAM for mitochondrial S-adenosylhomocysteine. This is the first report describing the identification and characterization of the human SAMC and its gene. (+info)
Theoretical analysis concerning the characteristics of a dye-binding method for determining serum protein based on protein error of pH indicator: effect of buffer concentration of the color reagent on the color development.
In the dye-binding method based on protein error of a pH indicator, the color development has been reported to be markedly affected by the buffer concentration of the color reagent. In this study, the author analyzed this phenomenon by a theoretical calculation based on the chemical equilibrium of protein error. The calculation was performed on the assumption that both the dissociated dye anion and the anion contained in the buffer solution react with protein, forming a dye-protein complex and an anion-protein complex, respectively. The calculated results were compared with those obtained by the experiments using bromophenol blue, bromocresol green and bromocresol purple that are employed widely for determining the human serum albumin concentration clinically. The calculated results of this method are summarized as follows: (1) the color development decreases with the increase in the concentration of the anion contained in the buffer solution; (2) the calibration curve is more linear in the higher concentration of the anion than in the lower one. These calculated results agreed well with the experimental ones. From these results, it was concluded that the change in the color development by the buffer concentration of the color reagent is due to the change in the concentration of the buffer anion. (+info)
Measuring albumin and calcium in serum in a dual test with the Hitachi 704.
We describe a method for simultaneously determining albumin, by using bromcresol purple, and calcium, by using Arsenazo III, in the same analytical cuvette on the Hitachi 704. Both assays agree well with accepted procedures. The standard curves for the albumin and calcium assays are linear from 0 to 60 g/L and 0 to 5.0 mmol/L, respectively. Calibration is stable for 7 days with use of open reagent in the instrument. Both assays are unaffected by hemoglobin less than or equal to 5 g/L and Intralipid less than or equal to 4 g/L; calcium is unaffected by bilirubin less than or equal to 600 mumol/L. (+info)