Relationship between Glomerular Filtration Rate and the Prevalence of Metabolic Abnormalities: Results from the Third National Health and Nutrition Examination Survey (NHANES III)

BACKGROUND AND AIMS: National Kidney Foundation Kidney Disease Outcomes Quality Initiative (KDOQI) guidelines recommend that all people with a glomerular filtration rate (GFR) <60 ml/min/1.73 m(2) undergo evaluation for anaemia and metabolic bone disease. We aim to report the prevalence of metabolic complications in adults with low GFR. METHODS: Analysis of 15,802 non-institutionalised adult participants in the Third National Health and Nutrition Survey (NHANES III), a cross-sectional population-based survey conducted in the United States between 1986 and 1994. Renal function was estimated according the modification of diet in renal disease equation 7 (MDRD GFR), the Cockcroft-Gault formula and by the serum creatinine cut-off points described by Couchoud and colleagues. Haemoglobin <110 g/l occurred in 42.2% [95% confidence interval (CI) 28.3-56.0] of patients with MDRD GFR <30 ml/min/1.73 m(2) [stage 3 chronic kidney disease (CKD)] and 3.5% (95% CI 2.4-4.7) of patients with MDRD GFR between 30 and 60 ml/min/1.73 m(2) (stage 4-5 CKD). Corresponding prevalences for calcium <2.15 mmol/l were 8.2 (95% CI 1.6-14.8) and 3.4 (95% CI 1.7-5.2); for phosphate >1.6 mmol/l, 15.1 (95% CI 5.0-25.3) and 0.3 (95% CI 0-0.6); and for bicarbonate <23 mmol/l, 32.7 (95% CI 19.6-45.9) and 5.7 (95% CI 3.3-8.2), respectively. Similar results were obtained when patients were categorised by the Cockcroft-Gault formula or Couchoud's cut-off points. CONCLUSIONS: The prevalence of complications in stage 3 CKD is low. These data do not support the recommendation for routine screening for metabolic complications of renal insufficiency in adults seen in primary care settings whose GFR exceeds 30 ml/min/1.73 m(2).