ImmunoDip: an improved screening method for microalbuminuria.

Background: It is important to test for microalbuminuria in patients with diabetes, hypertension and possible insulin resistance syndrome. Current screening methods are suboptimal. This study evaluates a new office screening test for microalbuminuria that utilizes a monoclonal antibody against human serum albumin (ImmunoDip).

Methods: 182 urine samples were collected from patients attending diabetes, nephrology or hypertension clinics. The ImmunoDip screening test was carried out in the 182 samples after which albumin and creatinine concentrations were measured quantitatively in a reference laboratory.

Results: Screening the 182 patient samples with ImmunoDip and designating an albumin:creatinine ratio of > or =30 microg/mg as positive yielded a sensitivity of 96%, a specificity of 80%, a positive predictive value (PPV) of 66% and a negative predictive value (NPV) of 98%. The reduced specificity and PPV were not due to an intrinsic inaccuracy with ImmunoDip screening of these samples, but rather was shown to be due to the discordance between the accepted upper limits of normal for the albumin:creatinine ratio (30 microg/mg) and the albumin concentration (20 mg/l), the latter corresponding to a ratio of 20 microg/mg. In 35 samples with albumin concentrations of 20-50 mg/l, ImmunoDip screening yielded only one false negative (FN) result.

Conclusions: ImmunoDip is an excellent screening tool for microalbuminuria.