Assessments of endothelial function and arterial stiffness are reproducible in patients with COPD

Figures & data

Table 1 Characteristics and blood chemistry of patients with COPD

Variable	COPD patients
n	17
Male/female	6/11
Age (years)	56±2
Height (cm)	166±3
Weight (kg)	86±4
BMI (kg/m^2)	32.0±1.9
SBP (mmHg)	130±4
DBP (mmHg)	77±3
FEV1 (L/min)	1.52±0.53
FEV1 (% predicted)	51.5±3.4
FEV1/FVC ratio (%)	54.8±3.8
Glucose (mg/dL)	99±4
Total cholesterol (mg/dL)	203±13
HDL cholesterol (mg/dL)	63±4
LDL cholesterol (mg/dL)	122±11
Triglycerides (mg/dL)	124±16
Hemoglobin (g/dL)	14.6±0.5
Hematocrit (%)	42.1±1.2
CRP (mg/L)	9.3±2.5
Ankle brachial pressure index (right)	1.19±0.1
Ankle brachial pressure index (left)	1.1±0.1
Plasma cotinine (ng/mL)	103±30
Trans-3-hydroxycotinine (ng/mL)	42±14

Note: Data are expressed as mean ± standard error of mean.

Abbreviations: BMI, body mass index; SBP, systolic blood pressure; DBP, diastolic blood pressure; FEV₁, forced expiratory volume in 1 second; FVC, forced vital capacity; HDL, high-density lipoprotein; LDL, low-density lipoprotein.

Table 2 Within-day (session A vs session B) and between-day (session A vs session C) reproducibility of endothelial function

Variable	Session A n=17	Session B n=17	Session C n=17	Within-day session A vs session B						Between-day session A vs session C
				Paired t-test	CV	CV′	ICC	r	BA plot	Paired t-test	CV	CV′	ICC	r	BA plot
Baseline diameter (cm)	0.33±0.01	0.33±0.01	0.33±0.01	0.97*	2.28*	0.01*	0.985;	0.972;	X*	0.28*	2.85*	0.01*	0.997;	0.960;	X*
							P<0.01*	P<0.01*					P<0.01*	P<0.01*
Peak diameter (cm)	0.35±0.01	0.35±0.01	0.37±0.14	0.80*	2.17*	0.01*	0.988;*	0.976;	X*	0.99*	2.71*	0.01*	0.998;	0.951;	X*
							P<0.01	P<0.01*					P<0.01*	P<0.01*
FMD (%)	5.5±0.5	5.4±0.9	4.7±0.7	0.84*	30.6*	1.16*	0.762;*	0.685;	X*	0.16*	38.12	1.32*	0.740;	0.610;	X*
							P<0.01	P<0.01*					P<0.01*	P<0.01*

Notes: The flow-mediated dilation (FMD) parameters analyzed show reproducibility both during the same day and between-days in patients with COPD. All of the variables evaluated meet at least five out of the six criteria required to confirm reproducibility. Data are expressed as mean ± standard error of mean. Paired t-test statistic (P-value), coefficient of variation (CV= SD/mean ×100); coefficient of variation prime (CV’= [100× SD]/[mean +100]); intra-class correlation coefficient (ICC); Pearson’s correlation coefficients (r). X in the Bland–Altman plot (BA plot) cell indicates acceptable plot.

* indicates acceptable reproducibility. Individual reproducibility assessments that meet the criteria are in bold.

Figure 1 Bland–Altman analysis plots illustrating no systematic bias and good within-day reproducibility.

Notes: Within-day (session A and session B) Bland–Altman plots for (A) baseline diameter, (B) peak diameter, and (C) flow-mediated dilation (FMD). Patients with COPD underwent two examinations during the same day (3 hours apart) to confirm within-day reproducibility of endothelial function. The x-axis shows the mean of each variable and the y-axis the difference between pairs. Solid lines represent systematic bias and dashed lines represent the 95% CI at two SD of the differences.

Figure 2 Bland–Altman analysis plots illustrating no systematic bias and good between-day reproducibility.

Notes: Between-day (session A and session C) Bland–Altman plots for (A) baseline diameter, (B) peak diameter, and (C) flow-mediated dilation (FMD). Patients with COPD underwent two examinations during 2 different days (at least 1 week after first visit) to confirm within-day reproducibility of endothelial function. The x-axis shows the mean of each variable and the x-axis the difference between pairs. Solid lines represent systematic bias and dashed lines represent the 95% CI at two SD of the differences.

Table 3 Within-day (session A vs session B) and between-day (session A vs session C) reproducibility of arterial stiffness

Variable	Session A n=17	Session B n=17	Session C n=17	Within-day session A vs session B						Between-day session A vs session C
				Paired t-test*	CV*	CV′*	ICC*	r*	BA plot*	Paired t-test*	CV*	CV′*	ICC*	r*	BA plot*
AIx (%)	31±2	33±2	31±3	0.14	9.88	2.3	0.887;	0.797;	X	0.96	10.4	2.3	0.862;	0.761;	X
							P<0.01	P<0.01					P<0.01	P<0.01
AIx75 (%)	33±2	32±3	31±2	0.60	11.3	2.3	0.847;	0.749;	X	0.32	9.27	2.1	0.873;	0.778;	X
							P<0.01	P<0.01					P<0.01	P<0.01
PWV (m/s)	8.6±0.9	8.8±0.9	8.5±0.7	0.37	2.74	0.2	0.988;	0.979;	X	0.70	4.68	0.4	0.963;	0.929;	X
							P<0.01	P<0.01					P<0.01	P<0.01

Notes: The arterial stiffness variables assessed in this study show a high reproducibility both during the same session and during different sessions in patients with COPD. All the variables analyzed meet six out of the six criteria required to confirm reproducibility. Data are expressed as mean ± standard error of mean. Paired t-test statistic (P-value), coefficient of variation (CV= SD/mean ×100); coefficient of variation prime (CV′= [100× SD]/[mean +100]); intra-class correlation coefficient (ICC); Pearson’s correlation coefficients (r); X in the Bland–Altman plot (BA plot) cell indicates acceptable plot.

* indicated acceptable reproducibility. Individual reproducibility assessments that meet the criteria are in bold.

Abbreviations: AIx, augmentation index; PWV, pulse wave velocity.

Figure S1 Bland–Altman analysis plots illustrating no systematic bias and good within-day reproducibility for (A) AIx, (B) AIx75, and (C) PWV. Notes: Solid lines represent systematic bias and dashed lines represent the 95% CI at two SD of the differences.

Abbreviations: AIx, augmentation index; PWV, pulse wave velocity; AIx75, AIx at 75 bpm.

Figure S2 Bland–Altman analysis plots illustrating no systematic bias and good between-day reproducibility for (A) AIx, (B) AIx75, and (C) PWV.

Note: Solid lines represent systematic bias and dashed lines represent the 95% CI at two SD of the differences.

Abbreviations: AIx, augmentation index; PWV, pulse wave velocity; AIx75, AIx at 75 bpm.