Circulating Complement C1q as a Novel Biomarker is Associated with the Occurrence and Development of COPD

Figures & data

Table 1 Characteristics of COPD Subjects and Non-COPD Controls

Characters	COPD Subjects (n=203)	Non-COPD Controls (n=191)	P-value
Male gender(%)			0.491
Age, years	68.43±7.96	68.80±9.12	0.674
BMI, kg/m^2	24.16±4.30	24.30±3.10	0.729
Smokers(%)	178(87.7)	59(30.9)	<0.001
Pack years	35.52±27.38	10.88±20.80	<0.001
Comorbidity-Cardiovascular(%)	46(22.7)	37(19.4)	0.424
Comorbidity-Diabetes(%)	22(9.9)	20(10.5)	0.906
Comorbidity-Hypertension(%)	65(32.0)	51(26.7)	0.247
Leukocyte count, 10^9/l	7.01±2.48	6.73±2.37	0.265
Percentage of neutrophils(%)	69.62±12.14	63.30±11.56	<0.001
Serum complement C1q, mg/l	150.88±29.38	182.40±31.60	<0.001

Abbreviation: BMI, body mass index.

Table 2 Factors Correlated with Serum C1q in COPD Subjects

	Rho	P-value
FEV1/FVC ratio	0.327	<0.001
Predicted FEV1%	0.379	<0.001
%LAA-950	−0.252	<0.001
Percentage of neutrophils	−0.155	0.027
ESR	0.089	0.205
D-dimer level	0.033	0.637
Leukocyte count	−0.011	0.880
Pack years	−0.072	0.304

Abbreviations: FEV1, forced expiratory volume in 1 second; FVC, forced vital capacity; %LAA, ratio of low attenuation areas; ESR, erythrocyte sedimentation rate.

Figure 1 Serum C1q showed a downward trend in COPD subjects (A), especially in GOLD 3–4 (B) and severe emphysema (C). Serum C1q was obviously positively correlated with the FEV1/FVC ratio and predicted FEV1% in COPD (D and E) but had a weakly negative correlation with the %LAA-950 (F). *P < 0.05, **P < 0.01, ***P < 0.001.

Abbreviations: ns, not significant; COPD, chronic obstructive pulmonary disease; FEV1, forced expiratory volume in 1 second; FVC, forced vital capacity; %LAA, ratio of low attenuation areas.

Figure 2 Serum C1q decreased in AECOPD subjects compared with stable COPD and non-COPD (A). Serum C1q was weakly negatively correlated with the percentage of neutrophils in peripheral blood in COPD subjects (B). ***P < 0.001.

Abbreviation: ns, not significant.

Table 3 Differences in the COPD Subjects Outcomes During 1-Year Follow-Up According to the Levels of Serum C1q on Admission

	All	C1q<137.150 mg/l	C1q≥137.150 mg/l	P-value
	N=144	N=53	N=91
Serious exacerbators (%)^a	44(30.6)	29(54.7)	15(16.5)	<0.001
Total number of serious exacerbations^a	85	57	28	-
Number of serious exacerbations/subject/year^a	0.590±1.067	1.057±1.200	0.319±0.880	<0.001
Deaths during follow-up (%)^a	12(8.3)	8(15.1)	4(4.4)	0.026

Note: ^ᵃEvents in the 1-year follow-up.

Figure 3 Serum C1q levels were downregulated in 44 follow-up severe exacerbators (A). Diagnostic accuracy of serum C1q to differentiate severe exacerbations in 144 follow-up COPD subjects (B). Area under the curves (AUC) was 0.762, and the cutoff value was set to 137.150 mg/L. Differences between subjects with low and high C1q levels in time to the next severe exacerbation (C) and time to death (D). ***P < 0.001.

Figure 4 C1q levels of smokers were lower than those of never-smokers, whether in COPD subjects (A) or all 394 subjects (B). *P < 0.05, ***P < 0.001.