Variability of plasma proteins according to molecular size. Long-term and short-term intra-individual variation

Abstract

The intra-individual variations in serum concentrations of α₁-antitrypsin, albumin and α₂-macroglobulin were determined using high precision analytical methods.

The long-term (3 months) variations were 8.2 % for α_1-antitrypsin and 2.9 % for α₂-macroglobulin in five males and five females. The coefficients of variation for albumin were 1.5 and 3.4% for males and females, respectively. In males the long-term variations of albumin and α₂-macroglobulin were highly correlated.

The short-term (2 days) intra-individual variations in six males were 2.5, 3.8 and 3.4% for α₁-antitrypsin, albumin and α₂-macroglobulin respectively (coefficients of variation). A diurnal variation was found for albumin with maximal concentrations at 18.00 hours. At 6.00 and 10.00 hours the fractional concentrations of α₁-antitrypsin and albumin were lower than for α₁-macro-globulin. The variations of the three proteins were positively correlated.

Key Words:

• albumin
• α₁-antitrypsin
• α₂-macroglobulin
• diurnal variation
• specific protein analysis—high precision
• individual vs analytical variation
• inter-protein variation
• sampling error
• tourniquet