The prevalence of undiagnosed renal failure in a cohort of COPD patients in western Norway.

Patients with COPD are at risk for other comorbid diseases, like heart failure, coronary heart disease, and depression. However, little is known about COPD phenotypes and prevalence of sub-clinical renal failure. 433 COPD patients and 233 subjects without COPD, from Western Norway, age 40-75, GOLD stage II-IV, were examined in 2006/07 upon entry to the Bergen COPD Cohort Study. Plasma creatinine was measured in 422 of the COPD patients. The Glomerular Flow Rate (GFR) was determined with the Cockcroft Gault formula, and having a GFR < 60 was defined as renal failure. Examined explanatory factors were sex, age, smoking habits, GOLD stage, hypoxemia, exacerbation history, cachexia, use of daily inhaled steroids, Charlson comorbidity score, use of ACE inhibitors and/or ARBs, and the inflammatory plasma markers C-reactive protein (CRP), soluble tumor necrosis factor receptor 1 (sTNF-R1) and neutrophil gelatinase associated lipocalin (NGAL). Associations between explanatory variables and renal failure were examined by a logistic regression analysis. The prevalence of having GFR < 60 was 9.6% in female COPD patients and 5.1% in male COPD patients (p = 0.08). In multivariable analysis, female sex, higher age, cachexia, and the inflammatory markers sTNF-R1 and NGAL were all independently associated with a higher risk for renal failure, whereas use of inhaled steroids, Charlson score, GOLD stage, respiratory failure, and exacerbation frequency were not. Undiagnosed renal failure is a concern particularly in elderly COPD patients and COPD patients with cachexia.