Functional and immunological concentrations of alpha 2-macroglobulin compared in plasma of subjects without alpha 1-protease inhibitor deficiency.

Alpha 2-Macroglobulin concentrations as measured by a functional assay and by laser nephelometry with antibody precipitation were compared for 67 outpatients at a respiratory clinic and 30 blood-donor control subjects with no respiratory disease. In both groups, concentrations of alpha 1-protease inhibitor in plasma, as measured by laser nephelometry, were within the normal reference interval. A reasonable correlation (r = 0.70) was obtained between results of functional assays and of laser nephelometry for the control individuals. For patients with pulmonary disease the correlation between the two assay methods was poorer (r = 0.53). We conclude that the functional assay of plasma is the better method for detecting abnormal concentrations of alpha 2-macroglobulin in patients with lung diseases.