Table 2.

Systematic review of 10 studies reporting prevalence of CKD in patients with COPD; excluded from meta-analysis

Study	Population	COPD diagnosis method & Definition of CKD	Methodological features	Results
Almagro et al., 2002 [17] Study design: prospective cohort study Funding: not reported	Setting & period: patients hospitalized to an acute-care hospital in Barcelona (Spain) for acute exacerbation of COPD, between October 1996 and May 1997 Patient group: 135 patients, 96% male, median age 72.2 ± 9.25 years	Diagnosis of COPD: Spirometry CKD definition: not defined, diagnosis information obtained from Charlson index	Selection bias: yes, patients admitted with COPD exacerbation Information bias: Objective outcome evaluation: no; standardized CKD risk measurement: no	4.4% of the patients are reported to have renal failure
Almagro et al., 2009 [18] Study design: Cross-sectional, multi-center study Funding:	Setting & period: patients admitted with COPD exacerbation to any of the participating 26 hospital centers throughout Spain, consecutively between January 1, 2007 and December 31, 2008 Patient group: 398 patients, 89% male, mean age of 73.7 years	Diagnosis of COPD: Spirometry CKD definition: not defined, comorbidity information obtained from Charlson index and an ad hoc questionnaire	Selection bias: patients admitted with COPD exacerbation Information bias: Objective outcome evaluation: no; standardized CKD risk measurement: no	6.5% of patients are reported to have moderate kidney failure
Almagro et al.; 2012 [16] Study design: Longitudinal, observational, multi-center study Funding: provided by Chiesi España	Setting & period: Patients hospitalized for COPD exacerbation to 70 ED and internal medicine services in Spain between October 2009 and October 2010 Patient group: 606 patients, 89.9% male, median age 72.6 years (range, 41-94)	Diagnosis of COPD: Spirometry CKD definition: not defined, diagnosis information obtained using Charlson index and a questionnaire	Selection bias: yes, patients admitted with COPD exacerbation Information bias: Objective outcome evaluation: no; standardized CKD risk measurement: no	15.5% of patients are reported to have Kidney disease with serum creatinine <3 0.7% of patients are reported to have Kidney disease with serum creatinine >3
Antonelli Incalzi et al., 1997 [19] Study design: Retrospective cohort study Funding: not reported	Setting & period: Consecutive patients discharged from Catholic University in Rome between the years 1980 and 1990, after an acute exacerbation of COPD Patient group: 270 patients, 83% male, mean age 67 ± 9 (SD) years	Diagnosis of COPD: Spirometry CKD definition: not defined, obtained from Charlson’s index	Selection bias: patients likely with severe COPD Information bias: Objective outcome evaluation: no; standardized CKD risk measurement: no	6.6% of patients were noted to have chronic renal failure Death in these patients was predicted by several variables including chronic renal failure (HR 1.79; 95% CI 1.05–3.02)
Chen et al.; 2016 [7] Study design: Case-Cohort study Funding: Ministry of Science of Technology, Taiwan	Setting & period: Patients aged 40 years or older who had inpatient hospitalization between 1998 and 2008 with Longitudinal Health Insurance Database (LHID) 2000 as the case group COPD group: 7,739 patients, 67.5% males, mean age 71.7 years Non-COPD group: 15,478 patients, 67.5% males, mean age 71.7 years	Diagnosis of COPD: Based on hospitalization for COPD CKD definition: Clinical diagnosis Blinding of outcome adjudicator: not reported	Selection bias: none Information bias: objective outcome evaluation: yes; standardized CKD risk measurement: yes Confounding: no Matching: yes. Adjustment in analysis: yes Confounding variables: yes; age, gender, first diagnosis of COPD Loss to follow up: none	Overall incidence of CKD was higher in COPD group than in non-COPD group. The adjusted hazard ratio of case was 1.61 (P <0.0001) times that of control.
Ford, E S.; 2015 [20] Study design: retrospective case-control study Funding: None	Setting & period: 5711 American men and women aged 40 to 79 years who participated in the Third National Health and Nutrition Examination Survey (NHANES III) during the term 1988 through 1994 and followed through 2006 COPD group: 1390 participants Non-COPD group: 4321 participants	Diagnosis of COPD: spirometry CKD definition: eGFR calculation using the Chronic Kidney Disease Epidemiology Collaboration equations Blinding of outcome adjudicator: not reported	Selection bias: no Information bias: objective outcome evaluation: yes; standardized CKD risk measurement: yes Confounding: no Matching: yes. Adjustment in analysis: yes Confounding variables: no Loss to follow up: none	The rates of incidence or prevalence of CKD was not reported. Comparative data on mean eGFR values in COPD group and Non-COPD group was reported. Adjusted mean levels of eGFR were significantly lower in adults with moderate-severe COPD (87.7 mL/min/1.73 m2) than in adults with normal lung function (89.6 mL/min/1.73 m2) (p = 0.015)
García-Olmos et al., 2013 [21] Study design: Observational, cross-sectional study Funding: CDTI/Ministry of Science and Innovation	Setting & period: practice population allocated to 129 Family Physicians, conducted in a health area of the Madrid Patient group: 3,183 patients, 76% male, mean age of 71.41 ± 11.50 years	Diagnosis of COPD: from clinical history in EMR CKD definition: not defined, obtained from EMR	Selection bias: not validated COPD diagnostic method Information bias: Objective outcome evaluation: no; standardized CKD risk measurement: no	6.34% of patients have chronic renal failure
Marti et al., 2005 [22] Study design: Retrospective cohort study Funding: In part by grant from Fundacio ‘noma’Catalana de Pneumologia and by Red Respira-ISCIII-RTIC-03/11	Setting & period: patients with COPD initiating LTOT >15 h/day during 1992–1999 in a tertiary teaching hospital (Vall d’Hebron Hospital, Barcelona, Spain) Patient group: 128 patients, 98.4% male, mean age ± SD 68.9 ± 9.7 years	Diagnosis of COPD: PFTs CKD definition: not defined, assessed using Charlson index	Selection bias: yes, COPD patients only on long term O2 therapy Information bias: Objective outcome evaluation: no; standardized CKD risk measurement: no	1.6% of patients are reported to have renal disease
Terzano et al., 2010 [23] Study design: Prospective longitudinal study Funding:	Setting & period: Consecutive COPD patients admitted to four hospitals in Italy for acute exacerbation from 1999 to 2000, and followed up until December 2007 Patient group: 288 patients, 78.8% male, mean age 69.2 years (SD ± 6.4)	Diagnosis of COPD: standardized CKD definition: not defined, assessed using Charlson index	Selection bias: yes, patients admitted for acute exacerbation Information bias: Objective outcome evaluation: no; standardized CKD risk measurement: no	26.3% of patients are reported to have chronic renal failure
Van Manen et al.; 2001 [24] Study design: case control study Funding: Boehringer Ingelheim NL supplied materials and personnel for performing lung function testing	Setting & period: Adults aged 40 years or more who visited outpatient practices in urban and suburban regions of western part of Netherlands from October 1996 through June 1997 COPD group: 290 patients (male 64.1%; mean age 65.8 years) Non-COPD group: 421 patients (male 41.1%; mean age 65.9 years)	Diagnosis of COPD: Pulmonary function tests CKD definition: not reported Blinding of outcome adjudicator: not reported	Selection bias: no Information bias: objective outcome evaluation: yes; standardized CKD risk measurement: no Confounding: no Matching: no Adjustment in analysis: yes Confounding variables: no Loss to follow up: none	The study population was surveyed to estimate the prevalence of a set of 23 diseases in patients with COPD compared to patients without COPD. Self-reported renal disease was included in general and no specifications on chronic kidney disease or renal failure was surveyed. Renal disease was reported 0.3% in patients with COPD compared to 0.2% in non-COPD patients