06 July 2004
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<sup>®</sup>). Methods: 182 urine samples were collected from patients attending diabetes, nephrology or hypertension clinics. The ImmunoDip<sup>®</sup> 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<sup>®</sup> and designating an albumin:creatinine ratio of ≧30 µg/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<sup>®</sup> 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 µg/mg) and the albumin concentration (20 mg/l), the latter corresponding to a ratio of 20 µg/mg. In 35 samples with albumin concentrations of 20–50 mg/l, ImmunoDip<sup>®</sup> screening yielded only one false negative (FN) result. Conclusions: ImmunoDip<sup>®</sup> is an excellent screening tool for microalbuminuria.