Background: As many subjects with a cardiovascular (CV) risk factor are undiagnosed, guidelines to prevent cardiovascular disease argue for case finding on those risk factors. Such an approach is, however, labour and cost intensive. An elevated urinary albumin loss is an early marker of vascular damage and is associated with an increased CV risk. As albuminuria is easy to measure, we tested whether a screening approach in which detailed risk factor measurement is done only after selection of subjects with an elevated albuminuria results in a higher yield of subjects at risk.
Methods: A random sample of the general population as investigated in the Prevention of Renal and Vascular End-Stage Disease study was used. Plasma glucose, blood pressure, serum cholesterol and renal function were measured in an overall random sample of the population, in subgroups according to their urinary albumin concentration (UAC) of one first morning urine void and in subgroups in whom the elevated albuminuria level was confirmed with two 24 h urine collections for measurement of urinary albumin excretion (UAE).
Results: In the overall population, the number of subjects with any newly found CV risk factor was higher than the number of subjects already known with any CV risk factor (n = 1331 versus 370; 39.2 versus 10.9%). The prevalence of subjects with any newly diagnosed CV risk factor was higher in the group of 267 subjects with a first morning UAC of ≥ 20 mg/L (61.0%; P < 0.05) compared to the overall population (39.2%). Although the sensitivity of a UAC ≥ 20 mg/L to detect a subject with at least one CV risk factor was relatively low (12%), the specificity was very high (96%). The positive predictive value was 70%. When the elevated UAC could be confirmed in two subsequent 24-h urine collections, the diagnostic yield still further improved.
Conclusion: The prevalence of undiagnosed CV risk factors in the general population is much higher than the prevalence of known risk factors. After a selection of subjects with an elevated albuminuria, the relative prevalence of subjects with newly diagnosed CV risk factors increases while the number of subjects to test for presence of CV risk factors is smaller. Such an approach facilitates a more effective and simple strategy for risk factor screening.