The standardization of a biochemical laboratory determination of multiple myeloma

Overview

Objective:
The standardization of the biochemical measurement procedures in a blood serum of patients with multiple myeloma concerning an implementation of a new international prognostic index, which uses only two laboratory markers, albumin and beta-2 microglobulin.

Design:
The study compares results of albumin, beta-2 microglobulin and partly the concentration of paraproteins from six cooperative centers, which provide treatment of the multiple myeloma in the Czech Republic in order to integrate these investigations.

Material and Methods:
The laboratories of university hospitals – General University Hospital of Prague, University Hospital of Prague – Vinohrady, Hradec Králové, Olomouc, Brno – Bohunice and Plzeň have been chosen for the implementation of the study. Each control serum sample was divided into six same parts and was frozen at -80 °C. The transportation of the samples to the single laboratory was performed in a frozen box and the samples were stored at least at -70 °C till the date of determination. The whole project lasted two years and step by step it was divided into three periods (2003–2005). In the first period the determination of albumin was standardized and the unsuitability of the RIA method determination of beta-2 microglobulin with other methods was proofed. In the second period the determination of beta-2 microglobulin was standardized successfully, but because of some technical defects it was not possible to use the samples for the determination of paraproteins concentration. In the third period of the study 12 samples of blood serums were distributed, always with one monoclonal immunoglobulin to determine its concentration.

Results:
The determination of albumin is well standardized, a confidence interval for 95% is between 5.9–6.1% (tolerance limit for external quality assessments up to 9%). The unification of methods managed a comparability of the results of beta-2 microglobulin. The variation coefficient is to the 15% (tolerance limit derived from biological variation of this analyte is up to 15.5%). The determination of monoclonal immunoglobulins concentration confirmed the known experience that it is impossible to consolidate the determination because of many partial uncertain steps. Nevertheless the study showed clinical usability and analytical comparability of the results from the single centers with the concentration of paraproteins over 20 g/l.

Conclusion:
The determination of albumin is well standardized and the results from all laboratories are comparable. The determination of beta-2 microglobulin after a methodical unification provides comparable results without any significant differences. The determination of the monoclonal immunoglobulins concentration provided comparable results especially in concentrations higher than 20 g/l. This determination is mostly questionable, but it is concerned to monitor reactive changes by every laboratory, therefore the integration of the results has not been actual so far.

Key words:
multiple myeloma, monoclonal immunoglobulin, albumin, beta-2 microglobulin, standardization