Table 2 Systematic review of 10 studies reporting prevalence of CKD in patients with COPD; excluded from meta-analysis

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