title: Prevalence of chronic kidney diseases in patients with chronic obstructive pulmonary disease: assessment based on glomerular filtration rate estimated from creatinine and cystatin C levels.
abstract: BACKGROUND
  Cardiovascular diseases, osteoporosis, and depression are identified comorbidities of chronic obstructive pulmonary disease (COPD), but there have been few reports of chronic kidney disease (CKD) as a comorbidity of COPD. The objective of this study was to investigate the prevalence of CKD in COPD patients using estimated glomerular filtration rate (eGFR) based on creatinine (Cr) and cystatin C (Cys) levels.
  
  
  METHODS
  The prevalence of CKD and the values of various CKD-related parameters were compared between 108 stable COPD outpatients (COPD group) and a non-COPD control group consisting of 73 patients aged 60 years or more without a history of COPD or kidney disease. CKD was defined as an eGFR less than 60 mL/min/1.73 m(2).
  
  
  RESULTS
  The Cr level was significantly higher in the COPD group, but eGFR based on serum Cr (eGFRCr) was not significantly different between the two groups (73.3±25.3 vs 79.7±15.5 mL/min/1.73 m(2)). The Cys level was significantly higher and eGFR based on serum Cys (eGFRCys) was significantly lower in the COPD group (60.0±19.4 vs 74.0±13.5 mL/min/1.73 m(2), P<0.0001). The prevalence of CKD evaluated based on eGFRCr was 31% in the COPD group and 8% in the non-COPD group with an odds ratio of 4.91 (95% confidence interval, 1.94-12.46, P=0.0008), whereas the evaluated prevalence based on eGFRCys was 53% in the COPD group and 15% in the non-COPD group with an odds ratio of 6.30 (95% confidence interval, 2.99-13.26, P<0.0001), demonstrating a higher prevalence of CKD when based on eGFRCys rather than on eGFRCr.
  
  
  CONCLUSIONS
  CKD is a comorbidity that occurs frequently in COPD patients, and we believe that renal function in Japanese COPD patients should preferably be evaluated based not only on Cr but on Cr in combination with Cys.
authors.affiliation: Department of Internal Medicine, Kanamecho Hospital, Toshima-ku, Tokyo, Japan ; Division of Respiratory Medicine, Department of Internal Medicine, Itabashi-ku, Tokyo, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Yoshizawa
authors.affiliation: Division of Nephrology, Hypertension and Endocrinology, Department of Medicine, Nihon University School of Medicine, Itabashi-ku, Tokyo, Japan.
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Okada
authors.affiliation: Department of Internal Medicine, Kanamecho Hospital, Toshima-ku, Tokyo, Japan ; Division of Respiratory Medicine, Department of Internal Medicine, Itabashi-ku, Tokyo, Japan.
authors.forename: Sachiko
authors.initials: S
authors.lastname: Furuichi
authors.affiliation: Department of Internal Medicine, Kanamecho Hospital, Toshima-ku, Tokyo, Japan.
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Ishiguro
authors.affiliation: Department of Internal Medicine, Kanamecho Hospital, Toshima-ku, Tokyo, Japan.
authors.forename: Akitaka
authors.initials: A
authors.lastname: Yoshizawa
authors.affiliation: Division of Respiratory Medicine, Department of Internal Medicine, Itabashi-ku, Tokyo, Japan.
authors.forename: Toshiki
authors.initials: T
authors.lastname: Akahoshi
authors.affiliation: Division of Respiratory Medicine, Department of Internal Medicine, Itabashi-ku, Tokyo, Japan.
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Gon
authors.affiliation: Division of Respiratory Medicine, Department of Internal Medicine, Itabashi-ku, Tokyo, Japan.
authors.forename: Tsuneto
authors.initials: T
authors.lastname: Akashiba
authors.affiliation: Department of Internal Medicine, Kanamecho Hospital, Toshima-ku, Tokyo, Japan ; Division of Respiratory Medicine, Department of Internal Medicine, Itabashi-ku, Tokyo, Japan.
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Hosokawa
authors.affiliation: Division of Respiratory Medicine, Department of Internal Medicine, Itabashi-ku, Tokyo, Japan.
authors.forename: Shu
authors.initials: S
authors.lastname: Hashimoto
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D015897:Comorbidity; D003404:Creatinine / Q000097:blood*; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007564:Japan / Q000453:epidemiology; D007668:Kidney / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D016017:Odds Ratio; D011237:Predictive Value of Tests; D015995:Prevalence; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000453:epidemiology*; D051436:Renal Insufficiency, Chronic / Q000097:blood / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology; D012307:Risk Factors
chemical_list: D015415:Biomarkers; C525030:CST3 protein, human; D055316:Cystatin C; D003404:Creatinine
keywords: CKD; COPD; comorbidity; eGFR