title: Alpha 1-acid glycoprotein decreases recovery of total protein in urine when trichloroacetic acid is used to precipitate the proteins.
abstract: Total urine protein was measured in 132 samples by an automated benzethonium chloride method and the Ponceau-S/trichloroacetic acid (PS/TCA) method. Of these, 27% gave a result 0.1 g/L or more higher by the benzethonium chloride method. Of this 27%, most contained an abnormally high concentration of the acute-phase reactant, alpha 1-acid glycoprotein. By assaying urine containing added alpha 1-acid glycoprotein and albumin, we found that alpha 1-acid glycoprotein causes the PS/TCA method to underestimate the total urine protein concentration, whereas the benzethonium chloride method is unaffected. Not all urinary albumin was precipitated by TCA when alpha 1-acid glycoprotein was present. Therefore, protein methods in which trichloroacetic acid is used as a concentrating step before the assay will underestimate total urine protein when the concentration of alpha 1-acid glycoprotein is high.
authors.affiliation: Department of Clinical Biochemistry, Queen Elizabeth II Medical Centre, Nedlands, Western Australia.
authors.forename: J P
authors.initials: JP
authors.lastname: Beilby
authors.forename: B A
authors.initials: BA
authors.lastname: O'Leary
mesh_terms: D001391:Azo Compounds; D001558:Benzethonium; D011232:Chemical Precipitation; D005188:False Negative Reactions; D006801:Humans; D007118:Immunoassay; D007202:Indicators and Reagents; D009961:Orosomucoid / Q000652:urine*; D011507:Proteinuria / Q000652:urine*; D014238:Trichloroacetic Acid
chemical_list: D001391:Azo Compounds; D007202:Indicators and Reagents; D009961:Orosomucoid; D001558:Benzethonium; D014238:Trichloroacetic Acid; C032756:ponceau S