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

Figures & data

Figure 1 Consolidated standards of reporting trials flowchart.

Notes: (A) COPD patient group. (B) Non-COPD patient group.
Abbreviations: COPD, chronic obstructive pulmonary disease; eGFR_Cr, estimated glomerular filtration rate based on Cr (mL/min/1.73 m²); eGFR_Cys, estimated glomerular filtration rate based on Cys (mL/min/1.73 m²).

Table 1 Patient characteristics

Characteristics	COPD patient group (n=108)	Non-COPD patient group (n=73)	P-value
Age, years	74.3±7.1	71.8±7.3	0.0214
Sex, males	90 (83.3)	36 (49.3)	<0.0001
BMI, kg/m^2	21.1±3.1	23.7±2.4	<0.0001
Smoking history			<0.0001
Nonsmoker	0 (0)	30 (41.1)
Past smoker	100 (92.6)	36 (49.3)
Current smoker	8 (7.4)	7 (9.6)
Pulmonary function
VC, % predicted	88.6±20.3
FEV1, % predicted	52.4±21.2
GOLD classification
1	10 (9)
2	37 (34)
3	27 (25)
4	34 (32)
Comorbidities and underlying diseases
Hypertension	50 (46.3)	48 (65.8)	0.0147
Diabetes mellitus	14 (13.0)	26 (35.6)	0.0005
Dyslipidemia	14 (13.0)	39 (53.4)	,0.0001
Cardiovascular diseases	45 (41.7)	15 (20.5)	0.0037
Liver diseases	7 (6.5)	3 (2.7)	NS
Gastrointestinal diseases	27 (25.0)	15 (20.5)	NS
Osteoporosis	28 (25.9)	10 (13.7)	NS
Depression	6 (5.6)	2 (2.7)	NS
Sleep apnea syndrome	2 (1.9)	3 (4.1)	NS
Bronchial asthma	23 (21.3)	3 (4.1)	0.001
Malignant tumor	15 (13.9)	4 (5.5)	NS

Note: Data are number of cases (percentage) or mean ± SD.

Abbreviations: BMI, body mass index; COPD, chronic obstructive pulmonary disease; FEV₁, forced expiratory volume in 1 second; GOLD, Global Initiative for Chronic Obstructive Lung Disease; NS, not significant; SD, standard deviation; VC, vital capacity.

Table 2 Blood biochemistry and estimated glomerular filtration rates

	COPD patient group (n=108)	Non-COPD patient group (n=73)	P-valuea
Hb (g/dL)	13.2±1.9	13.3±1.5	NS
BUN (mg/dL)	17.0±6.9	14.6±3.9	0.0062
Cr (mg/dL)	0.8±0.3	0.7±0.1	<0.0001
Cys (mg/L)	1.2±0.4	0.9±0.2	<0.0001
eGFRCr (mL/min/1.73m^2)	73.3±25.3	79.7±15.5	NS
eGFRCys (mL/min/1.73m^2)	60.0±19.4	74.0±13.5	<0.0001
BNP (pg/mL)	47.6 (39.0–58.0)	27.2 (2.15–34.4)	0.0004

Notes: Data are mean ± SD or geometric mean (95% CI).

a Unpaired t-test.

Abbreviations: BNP, brain natriuretic peptide; BUN, blood urea nitrogen; CI, confidence interval; COPD, chronic obstructive pulmonary disease; Cr, creatinine; Cys, cystatin C; eGFR_Cr, estimated glomerular filtration rate based on Cr; eGFR_Cys, estimated glomerular filtration rate based on Cys; Hb, hemoglobin; NS, not significant; SD, standard deviation.

Table 3 Prevalence of CKD in the COPD patient group and the non-COPD patient group

	COPD patient group (n=108)	Non-COPD patient group (n=73)	P-valuea	OR
eGFRCr < 60	33 (31)	6 (8)	0.0004	4.91 (1.94–12.46)
eGFRCys < 60	57 (53)	11 (15)	,0.0001	6.30 (2.99–13.26)

Notes: Data are number of cases (percentage) or geometric mean (95% CI).

a Fisher’s exact test.

Abbreviations: CI, confidence interval; CKD, chronic kidney disease; COPD, chronic obstructive pulmonary disease; eGFR_Cr, estimated glomerular filtration rate based on Cr (mL/min/1.73 m²); eGFR_Cys, estimated glomerular filtration rate based on Cys (mL/min/1.73m²); OR, odds ratio.

Table 4 Prevalence of CKD by GOLD classification

GOLD grade (n)	eGFRCr < 60	eGFRCys < 60
1 (10)	4 (40)	6 (60)
2 (37)	11 (29.7)	16 (43.2)
3 (27)	9 (33.3)	15 (55.6)
4 (34)	9 (26.5)	20 (58.8)
P-valuea	0.531	0.421

Notes: Data are number of cases (percentage), n=108.

a Cochran–Armitage trend test.

Abbreviations: CKD, chronic kidney disease; eGFR_Cr, estimated glomerular filtration rate based on Cr (mL/min/1.73 m²); eGFR_Cys, estimated glomerular filtration rate based on Cys (mL/min/1.73 m²); GOLD, Global Initiative for Chronic Obstructive Lung Disease.