Beta 2-glycoprotein-1 (apolipoprotein H) excretion in chronic renal tubular disorders: comparison with other protein markers of tubular malfunction.

Urinary beta 2-glycoprotein-1 was measured in 60 patients with conditions recognised as causing renal tubular impairment and compared with established markers of early tubular malfunction. Increased beta 2-glycoprotein-1 excretion was found in 49 (82%) of the subjects; raised excretion of alpha 1-microglobulin, retinol-binding protein, and beta 2-microglobulin was found in 46 (77%), 45 (75%), and 31 (52%), respectively, and increased urinary N-acetyl-beta-D-glucosaminidase activity in 32 of 54 of the subjects (59%). The increase was particularly pronounced in those with proximal tubule malfunction, although considerable variation occurred. beta 2-glycoprotein-1 was shown to be stable in urine over the physiological pH range, and it is concluded that its measurement provides a means of detecting chronic malfunction of the renal tubules that is marginally more sensitive than assays of alpha 1-microglobulin or retinol-binding protein, and more reliable than assays of beta 2-microglobulin or N-acetyl-beta-D-glucosaminidase.

A sandwich enzyme-linked immunosorbent assay for beta 2-glycoprotein I.

A solid-phase sandwich enzyme-linked immunosorbent assay for determining beta 2-glycoprotein I in urine has been developed. It has a working concentration range of 5-40 micrograms/L and a detection limit of approximately 1.4 micrograms/L. The within-plate coefficient of variation (CV) falls between 1.4% and 2.1%, and the between-batch CV ranges from 5.2 to 6.0%. Recovery of beta 2-glycoprotein I added to urine varies between 96 and 110%. The assay can also be used for determining beta 2-glycoprotein I in serum.