[Chronic renal failure and hypertension in community cardiology practice]

A sustained increase in the incidence of vascular nephropa-thies has been recently documented in western countries and correlated with aging. Renal failure is often ignored in patients with hypertension and its diagnosis made too late, at the stage of replacement therapy, with an increased mortality rate and prolonged hospitalization time. In clinical practice, the diagnosis of renal insufficiency is based on the measurement of serum creatinine, which depends on muscular mass, gender and age of the subject and is regulated by glomerular filtration. Therefore, serum creatinine level does not give a correct estimate of renal function. According to Good Clinical Practice recommendations, serum creatinine must be used to calculate creatinine clearance, a surrogate of glomerular filtration. To avoid methodological constraints of clearance measurement with precise urine recollection, the index proposed by Cockcroft and Gault is highly reliable and widely used.

An epidemiological survey has been carried out to measure the prevalence of renal insufficiency in hypertensive patients regularly followed by cardiologists. This open, transverse study compared estimates of renal function based upon serum creatinine level and creatinine clearance using the Cockcroft and Gault's formula. Among 1,000 private cardiologists randomly selected in metropolitan France, 707 entered the study. During the last week of May 2000, they included 2,100 hypertensive patients using a questionnaire describing individual patient's demographic and clinical characteristics.

The mean age of hypertensive patients was 65.9 +/- 12.2 years. They used antihypertensive drugs for a mean 10.3 +/- 7.7 years. The prevalence of renal failure, as defined by a creatinine clearance lower than 60 ml/min, was 32%, whereas 61% of the patients had a creatinine clearance below 80 ml/min. In contrast, 71% of the patients were subjectively considered to have a normal renal function. This discrepancy reflects underdiagnosis of mild to moderate renal failure. Hypertensive patients with renal failure did not present with excess cardiovascular risk factors and comorbidities when compared with those having a normal renal function. Prevalence of type 2 diabetes and hypercholesterolemia was similar in both groups.

The present study outlines the discrepancy between theoretical knowledge and practical assessment of renal insufficiency in handling hypertensive patients, in the particular setting of cardiologist practice. In order to suppress this gap, the Cockcroft and Gault formula must be widely used. It is suggested that body weight, in addition to gender and age, may be printed together with serum creatinine concentration on the biology form given to patient.