Preventing actin interference in immunonephelometric measurements of vitamin D-binding protein (Gc-globulin)

Immunonephelometric quantification of group-specific component protein in patients with acute liver failure

“…Use of D 1 antiserum can yield values for Gc protein that are decreased by as much as ϳ16% in samples containing an equimolar concentration of actin. 11 Using the standard antiserum to Gc protein currently available from Dako Corporation, we observed no significant effect (average maximum change from baseline of less than 5% at a [Gc] of 195 µg/mL) of actin in the measurement of Gc protein in samples containing Gc protein and a 1.3to 4-fold excess of actin (Fig. 2), despite the formation of Gc:actin complexes as evidenced by our immunoblotting data (not shown).…”

“…The analytical specificity of immunoassays for the measurement of Gc protein is dependent upon the nature of the antiserum used in these assays. Except for the polyclonal rabbit antiserum to human Gc protein obtained from Dako Corporation and designated as D 1 , which yields falsely decreased values for Gc protein concentration, Hu et al 11 have demonstrated, using several other antisera (e.g., those designated as D 2 , C 1 , or P 3 ) that actin does not interfere with in the immunonephelometric measurement of Gc protein concentration. Use of D 1 antiserum can yield values for Gc protein that are decreased by as much as ϳ16% in samples containing an equimolar concentration of actin.…”