Misura e identificazione delle componenti monoclonali plasmatiche: risultati di uno studio multicentrico internazionale
The measurement and the identification of plasma monoclonal proteins: results from an international multicentre study.

AUTORI

ABSTRACT

The measurement and the identification of plasma monoclonal proteins: results from an international multicentre study.

The measurement of monoclonal proteins (MP) is basic for diagnosis, risk stratification, and evaluation of the response to the therapeutic treatment of plasma cells dyscrasias and lymphoproliferative disorders. Quality specifications of the MP measurement have been evaluated in a multicentre study involving 14 clinical laboratories and 2 In vitro Diagnostics Companies across three continents. Aliquots of human serum pools with normal, hypo- and hyper γ-globulinemia spiked with different amounts of therapeutic monoclonal drugs migrating in the γ-globulin zone, mimicking a MP and serum aliquots with a MP migrating in β-globulin zone were distributed to participants. Two articles, published in Clinical Chemistry and Laboratory Medicine, reported detailed results emerging from the study; the most significant have been condensed in the present paper. The MP concentration, the amount of the co-migrating proteins, especially the polyclonal immunoglobulins background, and the MP migration pattern significantly affect accuracy and precision of the MP quantification. When MP is <1 g/L, the unacceptable imprecision and the loss of accuracy, strongly discourage to report any numeric data, even though the presence of MP in the serum protein electrophoresis (SPE) must be reported qualitatively. The two gating techniques, namely perpendicular drop (DP) and tangent skimming (TS), lead to overestimation and underestimation of small MP, respectively. All the tested SPE methods, two agarose gel- and one capillary zone electrophoresis, detected 100% of MP ≥1 g/L; as expected, the limit of detection of immunofixation and immunosubtraction were moderately more sensitive. The overall mean intra-laboratory coefficient of variation (CV) for MP ranging 1-10 g/L was found around 5.0%; thus, the monitoring of changes in MP level over time within the same laboratory is considered reliable provided that the intensity of the polyclonal background remains stable.

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