RESUMO
BACKGROUND: Although the epidemiology of subjects with end-stage renal disease is well-known in Spain, the prevalence of mild to moderate chronic kidney disease (CKD) in the general population is unknown. In order to measure this, it is necessary to carry out studies in the general population including those who are not health service patients. During epidemiology studies, the method of measuring glomerular filtration rate can change significantly the measurements of the prevalence of mild to moderate CKD. METHODS: Between 1997 and 2000, we performed a multi-phase descriptive polistratified epidemiological transversal study. The section of public chosen was between the ages of 15 and 85 living in the health area of western Valladolid (Spain). We calculated creatinine clearance using four methods: serum creatinine concentration, creatinine clearance using 24-hour urine samples adjusting the volume to the expected creatinuria with the Walser formulas, using the Cockcroft-Gault (CG) equation and applying the Modification of Diet in Renal Disease (MDRD) study abbreviated formula. We classified the level of kidney function, according to the National Kidney Foundation-Dialysis Outcomes Initiative (NFK-DOQI) guidelines. RESULTS: The instances of stages 2 and 3 CKD rise with age and are more common in women than men. This tendency is apparent in middle age and persons of 65 and above. Using the CG method, almost half the old women had a stage 3 CKD as opposed to a third of the men. If the measurement is performed using the abbreviated MDRD study, there are very few differences between the sexes. The prevalence of stage 3 CKD is similar (around 8%) but the prevalence of stage 2 CKD rises to 60% as opposed to 36% calculated using the CG equation. After comparing the results obtained with those of the third National Health and Nutrition Examination Survey Study (see table VII), the measurements of stage 3 CKD using the CG formula or by means of expected creatininuria coincide relatively, although the prevalence of stage 2 CKD is higher in persons of 65 and over. If we use the abreviated MDRD study, the prevalences increase by more than 20%. CONCLUSIONS: The prevalence of stages 2 and 3 CKD is clearly influenced by the method of calculation used. The prevalence of stage 2 CKD affects at least a third of the general population while those affected by stage 3 CKD are between 3.3% and 8.5%.
