title: Improved between-laboratory agreement for specific protein assays in serum following introduction of a common reference preparation (SPS-01) demonstrated in an external quality assessment scheme.
abstract: Between-laboratory agreement for 6 specific protein assays was better in two surveys (total 8 specimens) in which a calibration material was provided than in the preceding five surveys (20 specimens) in a national external quality assessment scheme. CVs for immunoglobulins G, A and M (200 participants) and alpha 1-antitrypsin and complement components C3 and C4 (70 participants) were reduced from 18.3% (range 11.6-23.8%) to 10.7% (range 7.5-13.6%). This improvement was not due to changes in within-laboratory precision or in the concentrations of protein surveyed. Improvement was maintained in the following four surveys (3 normal and 5 pathological sera) without calibration material for immunoglobulins G and A and for alpha 1-antitrypsin. Agreement for immunoglobulin M, C3 and C4 returned to values close to the original CVs, but subsequently improved. The role of a common calibration material in improving between-laboratory agreement is discussed.
mesh_terms: D001798:Blood Proteins / Q000032:analysis*; D003176:Complement C3 / Q000032:analysis; D003181:Complement C4 / Q000032:analysis; D006801:Humans; D007136:Immunoglobulins / Q000032:analysis; D007753:Laboratories / Q000592:standards*; D011786:Quality Control; D012015:Reference Standards; D000515:alpha 1-Antitrypsin / Q000032:analysis
chemical_list: D001798:Blood Proteins; D003176:Complement C3; D003181:Complement C4; D007136:Immunoglobulins; D000515:alpha 1-Antitrypsin