INTRODUCTION

Renal function abnormalities are associated with high cardiovascular risk. This increased risk has been shown for all ranges of renal failure, not only for patients with end-stage renal failure, but also for those with a mild or moderate reduction in glomerular filtration rate (GFR)1,2 or with increased urinary albumin excretion or microalbuminuria (MAU).3-5 As a result of these findings, the major international societies recommend in their clinical guidelines that the presence of positive MAU or an estimated GFR < 60 ml/min be considered as a major cardiovascular risk factor.6-8

Simple and sensitive methods have now been developed for detecting renal function abnormalities. Determination of MAU allows the detection of target organ damage and indicates the presence of microcirculation impairment, as well as permitting the monitoring of treatment and the choice of drug therapy.9 GFR is the best method for measuring overall renal function. The use of formulas such as the one derived from the Modification in Diet in Renal Disease (MDRD) Study10 or the one proposed by Cockcroft and Gault11 allows a more precise approximation of renal function than a single determination of serum creatinine or creatinine clearance, while also reducing the technical complications and discomfort for the patient compared to clearance.12 The renal function assessment, in addition to its interest for stratifying the cardiovascular and renal risk of the patients, has important implications
for their follow-up and treatment.

Arterial hypertension and other forms of clinical presentation of cardiovascular disease are closely linked to the development of chronic renal disease, and play a key role in the development, clinical course and subsequent management of this disease. Determination of renal function is mandatory for risk stratification and the therapeutic approach to hypertensive patients. There are no studies to date assessing whether determination of renal function is performed adequately in clinical practice in hypertensive patients. The primary aim of this study was to assess the proportion of patients attended in cardiology outpatient clinics in whom MAU and/or GFR had been determined at least once in the previous 12 months. As a secondary aim, it sought to determine the association of these renal markers with cardiovascular risk factors and cardiovascular morbidity.

MATERIALS AND METHODS

Design

This was an observational, cross-sectional, retrospective, multicenter study. There was no drug intervention. The study was carried out in 1,224 hypertensive patients recruited consecutively in cardiology outpatient clinics. A total of 124 centers in Spain participated in the study. Each investigator included a total of 10 patients, who were the last 10 patients seen in the clinic with a diagnosis of arterial hypertension who met the inclusion criteria and none of the exclusion criteria. The inclusion criteria were patients age 18 years or over and a confirmed diagnosis of arterial hypertension. The exclusion criteria were patients with known renal disease with serum creatinine > 2.0 mg/dl, hospitalized patients, and patients with a life expectancy < 3 months. The study was approved by the Independent Ethics Committee of Hospital Universitario de San Juan.

Data collection

The following data were collected using a questionnaire: age, sex, weight, height, history of arterial hypertension, diabetes, dyslipidemia, smoking, obesity, sedentarism, presence of cardiovascular diseases or family history of cardiovascular disease. In addition, anthropometric measures were taken including height, weight, body mass index and abdominal circumference. Obesity was considered as a body mass index of 30 kg/m2 or greater. The presence of left ventricular hypertrophy was defined according to Sokolow-Lyon electrocardiographic criteria (voltage sum SV1+RV5 or RV6 > 35 mm). Biochemical data were obtained from the last laboratory test performed in the 6 months prior to collection of the study data. Determination of MAU and determination or calculation of GFR and the method used for each was assessed. Blood pressure was taken according the standard guidelines with a mercury
sphygmomanometer. After the patient had remained seated for 5 minutes, 3 blood pressure measurements were taken each 2 minutes apart. The average of the last 2 measurements was obtained and considered the patient¿s blood pressure.

Statistical analysis

Continuous variables was expressed as mean ± standard deviation and compared using Student¿s t test for unpaired data or the Welch test if the homocedasticity of the variances was significantly different. Normality of the distribution was checked using stem and leaf plots. Categorical variables were expressed as percentage of the study population and compared with the X2 test.

In the case of MAU, since it was a variable not calculable a posteriori, the analyses were performed based on the values provided by the investigators. In the case of GFR, the analyses were performed from the values calculated with the MDRD equation, which allowed the analysis of 87% of patients versus 11% of patients with GFR provided by the investigator.

Logistic regression models were adjusted to explain the variables independently associated with the active search for renal dysfunction. The adjusted odds ratios (OR) and their 95% confidence intervals (CI) are presented. Variables with proven clinical relevance and those with a significance level in the univariate analysis < 0.1 were included.

In all hypothesis contrasts&