Interleukin-6 is a Strong Predictor of the Frequency of COPD Exacerbation Within 1 Year

Figures & data

Figure 1 Study scheme.

Abbreviations: COPD, chronic obstructive pulmonary disease; IL-6, interleukin 6.

Table 1 Characteristics of COPD Patients (n=95)

Variable	Mean/N/Median	SD/%/IQR
Demographic
Age (years-old; median, IQR)	72.00	15.00
Male (N, %)	63	66.32
BMI (kg/m^2; median, IQR)	19.60	2.37
Smoking status (N, %)
Smoker	69	72.63
Ex-smoker	12	12.63
Clinical
Course of disease (years; median, IQR)	10.00	5.00
Frequency of acute exacerbation in the past 1 year (median, IQR)	1.00	1.00
Exacerbation frequency ≥ 2	35	36.84
CAT score (median, IQR)	18.00	7.00
mMRC score (median, IQR)	2.00	1.00
Lung Function
FEV1 (L; median, IQR)	1.20	0.60
FEV1%pred (median, IQR)	57.21	16.28
FEV1/FVC% (mean, SD)	53.94	7.85
Hematological Indicators
WBC (×10^9; mean, SD)	8.26	1.97
NE (×10^9; median, IQR)	5.63	2.28
EO (×10^9; median, IQR)	0.10	0.41
hs-CRP (mg/L; median, IQR)	5.50	6.64
IL-6 (pg/mL; median, IQR)	8.80	26.07

Notes: Normal range of WBC, NE, EO, hs-CRP and IL-6 (3.5~9.5×10⁹, 1.8~6.3×10⁹, 0.02~0.52×10⁹, 0~5 mg/L, 0~7 pg/mL).

Abbreviations: IQR, interquartile range (25th–75th percentile); N, number; SD, standard deviation; BMI, body mass index; CAT, chronic obstructive pulmonary disease assessment test; mMRC, modified British medical research council; FEV₁, forced expiratory volume in 1 second; FEV₁%pred, FEV₁ as a percentage of the predicted value; FVC, forced vital capacity; WBC, white blood cell count; NE, absolute neutrophil count; EO, absolute eosinophil count; hs-CRP, hypersensitive C reactive protein; IL-6, interleukin-6.

Table 2 Correlation Between hs-CRP, IL-6 and Clinical Data

Variables	hs-CRP		IL-6
	r	P	r	P
Frequency of acute exacerbation in the past 1 year	0.572	0.000	0.852	0.000
CAT score	0.559	0.000	0.850	0.000
mMRC score	0.363	0.000	0.684	0.000
FEV1%pred	−0.556	0.000	−0.948	0.000
FEV1/FVC%	−0.388	0.000	−0.522	0.000

Note: P<0.05 considered significant.

Abbreviations: CAT, chronic obstructive pulmonary disease assessment test; mMRC, modified British medical research council; FEV₁, forced expiratory volume in 1 second; FEV₁%pred, FEV₁ as a percentage of the predicted value; FVC, forced vital capacity; hs-CRP, hypersensitive C reactive protein; IL-6, interleukin-6.

Table 3 Risk Factors of the Frequency of Acute Exacerbation of COPD ≥ 2 Using Binary Regression Analysis

Variables	OR	95% CI	P
hs-CRP	0.110	0.901–1.382	0.313
IL-6	0.260	1.140–1.475	0.000

Abbreviations: hs-CRP, hypersensitive C reactive protein; IL-6, interleukin-6; OR, odds ratio; CI, confidence interval.

Figure 2 ROC analysis of IL-6 in predicting the frequency of acute exacerbation of COPD ≥ 2.

Abbreviations: IL-6, interleukin 6; AUC, the area under the curve.

Table 4 Compared the Frequency of Acute Exacerbation Between Different Groups After One-Year Follow-Up

Variables	Low IL-6 Group (n=36)	High IL-6 Group (n=29)	P value
Demographic
Age (years-old; mean, SD)	67.97 ± 1.47	68.27 ± 1.58	0.864
Male (N, %)	25, 69.44	19, 65.52	0.736
BMI (kg/m^2; mean, SD or median, IQR)	20.40 ± 0.33	21.71, 5.32	0.078
Smoker (N, %)	31, 86.11	22, 75.86	0.290
Clinical
Frequency of acute exacerbation in 1 year (median, IQR)	1.00, 1.00	2.00, 1.00	0.000
Exacerbation frequency ≥ 2 (N, %)	14, 38.89	23, 79.31	0.001
CAT Score (mean, SD)	19.77 ± 0.54	20.14 ± 0.66	0.735
mMRC Score (median, IQR)	2.00, 1.00	3.00, 1.00	0.268
Lung Function
FEV1%pred (mean, SD)	42.46 ± 1.81	40.04 ± 1.90	0.391
FEV1/FVC% (mean, SD)	49.00 ± 1.31	48.75 ± 1.30	0.838
Hematological Indicators
IL-6 (pg/mL; median, IQR)	6.73, 0.62	32.07, 26.67	0.000

Abbreviations: IQR, interquartile range (25th–75th percentile); N, number; SD, standard deviation; BMI, body mass index; CAT, chronic obstructive pulmonary disease assessment test; mMRC, modified British medical research council; FEV₁, forced expiratory volume in 1 second; FEV₁%pred, FEV₁ as a percentage of the predicted value; FVC, forced vital capacity; IL-6, interleukin-6.