Albumin as an outcome measure in haemodialysis in patients: the effect of variation in assay method

Autor: Paul Garrick, Graham Warwick, Alison Carfray, Paul Whitaker, Graeme J. Griffiths, Kieran Patel
Rok vydání: 2000
Předmět:
Zdroj: Nephrology, dialysis, transplantation : official publication of the European Dialysis and Transplant Association - European Renal Association. 15(11)
ISSN: 0931-0509
Popis: Introduction Background. Serum/plasma albumin is an important predictor of future mortality/morbidity in haemo- Serum/plasma albumin is an important predictor of dialysis (HD) patients and has been proposed as an future mortality/morbidity in patients with renal failure important audit measure. Different methods of albu- [1,2]. This predictive power is a reflection of the effect min assay give different results and the bias between of inflammation (albumin is a negative acute phase methods may be greater in renal failure patients. reactant) and malnutrition on albumin concentration Methods. Albumin concentration in plasma was meas- [3]. Hypoalbuminaemia is a marker for patients who ured by three methods, two dye-binding methods (bro- are unwell for other reasons (e.g. malignancy, infection, mocresol green (BCG) and bromocresol purple (BCP)) severe vascular disease), who are malnourished or both. There are no data to prove that interventions and an immuno-turbidimetric (ITM ) method, in 143 directed to raising serum albumin could improve the HD patients (group I ) and 49 non-renal patients outcome in these patients. A number of authorities (group II ). Comparisons were made between means, have recommended the audit of albumin concentravariation in differences across a range of albumin tions as an outcome measure of dialysis treatment. The concentrations and on the percentage of patients within Renal Association standards document [4] recomthe normal range. mends that serum albumin should be ‘within the Results. In HD patients (group I ), BCG over- normal range quoted by the local pathology laboratestimated plasma albumin compared with the other ory’ and this has been used as an important outcome two methods. The difference could be as much as 10 g/l measure in the first report of the UK Renal Registry and was more marked in hypoalbuminaemic patients. [5]. The use of the local range recognizes that a number The BCP method gave results closer to the ITM of different assay methods are used for measuring method, particularly in HD patients. These differences albumin and that these methods give different results were less marked in group II patients but both meth- [6 ]. We have noted that there are often major difods overestimated albumin compared with the ITM ferences in albumin measurements between two labmethod. Using the BCG local laboratory normal range, oratories routinely analysing samples from our haemo84% of HD patients had plasma albumin concentra- dialysis ( HD) patients. These laboratories use different tions within the normal range but this fell to 57% if assay methods but have similar normal ranges. the BCP results were used. However, we have found consistently that albumin Conclusions. The method for determining albumin concentrations, determined by the bromocresol purple concentration has a marked effect on the results par- (BCP) dye-binding method, are lower than the bromticularly in HD patients. BCG, the most commonly ocresol green (BCG) dye-binding method. These used method, gives higher results than other methods differences have been reported in renal failure patients and correlates poorly with an immunological method. before [7–10]. In this study, we sought to characterize These differences make comparative audit between the magnitude of the difference in a larger population, nephrology units difficult and have implications for compared with a ‘gold standard’ method for albumin other biochemical variables and other specialties. assay based on an immunological method. We also assessed the effect of different assay methods on the
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