American Journal of Respiratory and Critical Care Medicine

Rationale: Small studies have suggested that inhaled corticosteroids can suppress systemic inflammation in chronic obstructive pulmonary disease (COPD).

Objectives: To determine the effect of inhaled corticosteroids with or without long-acting β2-adrenergic agonist on systemic biomarkers of inflammation.

Methods: We conducted a double-blind randomized placebo-controlled trial across 11 centers (n = 289 patients with FEV1 of 47.8 ± 16.2% of predicted) to compare the effects of inhaled fluticasone alone or in combination with salmeterol against placebo on circulating biomarkers of systemic inflammation over 4 weeks. The primary endpoint was C-reactive protein (CRP) level. Secondary molecules of interest were IL-6 and surfactant protein D (SP-D).

Measurements and Main Results: Neither fluticasone nor the combination of fluticasone/salmeterol had a significant effect on CRP or IL-6 levels. There was, however, a significant reduction in SP-D levels with fluticasone and fluticasone/salmeterol compared with placebo (P = 0.002). Health status also improved significantly in both the fluticasone and fluticasone/salmeterol groups compared with placebo, driven mostly by improvements in the symptom scores. Changes in the circulating SP-D levels were related to changes in health status scores. FEV1 improved significantly only in the fluticasone/salmeterol group compared with placebo.

Conclusions: ICS in conjunction with long-acting β2-adrenergic agonist do not reduce CRP or IL-6 levels in serum of patients with COPD over 4 weeks. They do, however, significantly reduce serum SP-D levels. These data suggest that these drugs reduce lung-specific but not generalized biomarkers of systemic inflammation in COPD.

Clinical trial registered with www.clinicaltrials.gov (NCT 00120978).

Scientific Knowledge on the Subject

Small studies suggest that inhaled corticosteroids can reduce systemic inflammation in chronic obstructive pulmonary disease.

What This Study Adds to the Field

This large multicenter trial shows that inhaled corticosteroids with or without long-acting β2-agonist do not reduce C-reactive protein but do diminish surfactant protein D levels.

Chronic obstructive pulmonary disease (COPD) represents an increasing burden worldwide and, by 2020, its mortality rate will rank third, only behind stroke and heart disease (1). Although this figure is alarming, it is likely to be a gross underestimate of the true health and economic burden of COPD because COPD is an important risk factor for other common causes of morbidity and mortality, including cardiovascular disorders and lung cancer (2, 3). Although the pathobiology of COPD has not been fully elucidated, there is a growing recognition that systemic inflammation may play a salient role in COPD progression and morbidity (4). Systemic inflammation has been linked particularly with some extrapulmonary manifestations of COPD, including sudden deaths, arrhythmias, strokes, myocardial infarction, cancer (57), muscle weakness, reduced exercise tolerance, and poor health status (8). These data raise the possibility that treatments modulating systemic inflammation could improve important health outcomes in COPD. Inhaled corticosteroids with or without long-acting β2-adrenoceptor agonists (LABAs) reduce exacerbations and improve health status in COPD (9). Some studies suggest that they may also reduce systemic inflammation in COPD (10, 11), but these studies were limited by the observational nature of the study design and small sample sizes. The primary aim of this randomized, placebo-controlled, double-blind, multicenter clinical trial involving 11 centers in western Canada was to determine whether inhaled corticosteroids alone or in combination with a LABA reduce systemic inflammation in subjects with stable COPD.

See the online supplement for full details of methods used.

Rationale for Measurements

This trial was a double-blind randomized controlled trial comparing the effects of inhaled fluticasone alone or in combination with salmeterol against placebo on three circulating biomarkers. The primary endpoint was C-reactive protein (CRP). Secondary molecules of interest were IL-6 and surfactant protein D (SP-D). CRP was chosen because it is a robust (but nonspecific) marker of systemic inflammation and has been associated with clinical outcomes such as hospitalization and mortality in patients with stable COPD (6, 12). IL-6 was chosen because it has been associated with adverse clinical outcomes in the general community (13) and is the main cytokine regulator of CRP synthesis in the liver (14). Although both CRP and IL-6 are generally accepted biomarkers of systemic inflammation, their use in COPD may be limited because they are produced predominantly in nonpulmonary organs and therefore lack specificity for COPD outcomes. SP-D, on the other hand, is mainly secreted by alveolar type II pneumocytes and its circulating levels increase with lung injury (15). Elevated circulating levels of SP-D have also been associated with poor outcomes, including death, in such patients (16). SP-D was thus chosen to evaluate the effects of the drugs on lung inflammation and injury.

Study Participants

All participants had a clinical diagnosis of COPD (17). Spirometric criteria included FEV1 of less than 80% of predicted with an FEV1 to FVC ratio of less than 0.70 (post-bronchodilator values).

Overview of the Trial Design

Study participants underwent a run-in phase during which they received fluticasone (500 μg twice daily) for 4 weeks. This was followed by a medication withdrawal phase wherein inhaled corticosteroids, LABAs, and theophylline products were withdrawn for 4 weeks. All other medications, including short-acting β2-adrenoceptor agonists, anticholinergics, and tiotropium, were permitted during all phases of the study. Participants were then randomly assigned to one of three arms: placebo, inhaled fluticasone (500 μg twice daily) or inhaled fluticasone/salmeterol combination (500/50 μg twice daily) (Advair Diskus; GlaxoSmithKline, Mississauga, ON, Canada). Randomization was performed centrally and stratified according to current smoking status with allocation concealment in a 1 (placebo arm) to 2 (fluticasone arm) to 2 (fluticasone/salmeterol) distribution ratio.

Outcome Measurements

From serum samples, the participants' CRP, IL-6, and SP-D levels were determined in triplicate. In addition, during each visit, the participants completed the St. George's Respiratory Questionnaire (SGRQ) (18) and performed spirometry (19). Exacerbations were defined as worsening of COPD symptoms leading to hospitalization, a visit to the emergency room, or use of an antimicrobial agent and/or systemic corticosteroids as an outpatient.

Statistical Analysis

Analyses were conducted based on an intention-to-treat principle and based on actual measurements: no data were imputed. The baseline characteristics of the study subjects were compared using a χ2 test with appropriate degrees of freedom for dichotomous variables and one-way analysis of variance for continuous variables. Tukey's post hoc analysis was used to adjust for multiple (pairwise) comparisons. For nonnormally distributed variables, a Kruskal-Wallis test was used. The multiple Behrens-Fisher test (20) was used to adjust for multiple (pairwise) comparisons of nonnormally distributed variables. All statistical tests were two-tailed in nature and P < 0.05 was considered statistically significant (SAS version 9.1; SAS Institute, Cary, NC). Normally distributed continuous variables are reported as mean ± SD, whereas nonnormally distributed variables are reported as median (interquartile range) unless otherwise indicated.

A total of 356 subjects were screened. Of these, 67 were excluded because they failed to meet the inclusion and exclusion criteria of the study, leaving 289 subjects for analysis. Between visits 1 and 2, 29 subjects dropped out of the study and 36 dropped out between visits 2 and 3, mostly because of worsening in their symptoms or heath status. This left 224 subjects, who were randomized at visit 3 into three arms of the trial: 45 to the placebo, 87 to fluticasone and 92 to fluticasone/salmeterol combination groups. A flow diagram summarizing the distribution of the subjects is shown in Figure 1. The baseline characteristics of the study participants at each of the major visits are shown in Table 1.

TABLE 1. BASELINE CHARACTERISTICS OF SUBJECTS AT EACH PHASE OF THE STUDY




Run-in (n = 289)

Withdrawal (n = 260)

Randomized Treatment (n = 224)
Age, yr68.8 ± 9.068.8 ± 9.169.3 ± 9.3
Men, %60.261.263.0
BMI, kg/m227.7 ± 6.027.7 ± 6.027.4 ± 5.8
Current smoker, %32.531.529.9
Pack-years*56.356.057.6
(43.0–73.0)(42.5–73.5)(43.0–77.5)
FEV1, L1.36 ± 0.541.39 ± 0.561.38 ± 0.57
FEV1, % predicted47.8 ± 16.248.3 ± 16.847.4 ± 15.9
FVC, L2.82 ± 0.872.84 ± 0.912.81 ± 0.85
FVC, % predicted75.3 ± 16.575.7 ± 18.674.4 ± 16.3
CRP*, mg/L3.373.132.90
(1.52–6.80)(1.68–7.09)(1.49–6.82)
IL-6*, pg/ml2.232.282.32
(1.54–3.64)(1.56–3.43)(1.54–3.58)
SP-D*, ng/ml104.5105.7116.0
(76.0–143.5)(80.0–138.5)(85.6–148.1)
SGRQ
 Total score42.4 ± 16.540.4 ± 16.741.6 ± 17.0
 Symptoms score49.6 ± 22.246.0 ± 22.452.2 ± 22.5
 Activity score60.2 ± 20.159.2 ± 21.360.0 ± 22.0
 Impacts score
29.9 ± 17.1
27.8 ± 16.9
27.9 ± 17.2

Definition of abbreviations: BMI = body mass index; CRP = C-reactive protein; SGRQ = St. George's Respiratory Questionnaire; SP-D = surfactant protein D.

Data are shown as mean ± SD, unless indicated otherwise.

*Nonnormally distributed variables are shown as median (interquartile range).

Visit 1 (Enrollment)

The average age of the subjects was 68.8 ± 9.0 years; 60.2% were males and 32.5% were current smokers. The average body mass index was 27.7 ± 6.0 kg/m2 and the average FEV1 was 1.36 ± 0.54 L or 47.8 ± 16.2% of predicted. A total of 58.4% of subjects were taking combination therapy, whereas 68.3% were taking an inhaled corticosteroid–containing drug at the time of enrollment. The average total SGRQ score was 42.4 ± 16.5 units. The median (interquartile range) SP-D was 104.5 (76.0–143.5) ng/ml, CRP was 3.4 (1.5–6.8) mg/L, and IL-6 was 2.2 (1.5–3.6) pg/ml.

Visit 2 (Run-in Phase; 1 mo of Fluticasone)

The changes in the serum biomarkers across the various phases of the study relative to baseline are summarized in Table 2. After 1 month of fluticasone, the subjects' CRP changed by a median (interquartile range) of 0.0 (−1.0 to 1.3) mg/L (P = 0.325); IL-6 changed by 0.0 (−0.6 to 0.6) pg/ml (P = 0.924) and SP-D changed by 1.3 (−9.1 to 13.3) ng/ml (P = 0.178); FEV1 changed by −0.6 (−3.8 to 4.2) % predicted (P = 0.779); and SGRQ changed by −1.7 (−6.7 to 4.5) units (P = 0.012).

TABLE 2. CHANGES IN CIRCULATING BIOMARKERS, HEALTH STATUS AND LUNG FUNCTION OF SUBJECTS DURING THE RUN-IN AND MEDICATION WITHDRAWAL PHASES OF THE STUDY



Run-in

Withdrawal

n = 260
P Value*
n = 224
P Value*
CRP, mg/L0.0 (−1.0 to 1.35)0.3250.0 (−1.3 to 1.3)0.829
IL-6, pg/ml0.0 (−0.6 to 0.6)0.924−0.1 (−0.6 to 0.6)0.728
SP-D, ng/ml1.3 (−9.1 to 13.3)0.1785.6 (−4.5 to 20.1)<0.001
SGRQ
 Total score−1.7 (−6.7 to 4.5)0.0122.6 (−2.3 to 8.1)<0.001
 Symptoms score−2.3 (−12.9 to 8.6)0.0396.1 (−4.4 to 17.0)<0.001
 Activity score0.0 (−6.7 to 6.2)0.3780.0 (−6.0 to 6.8)0.015
 Impacts score−1.6 (−7.7 to 5.2)0.0311.6 (−4.2 to 8.3)0.010
FEV1, % predicted−0.6 (−3.8 to 4.2)0.779−1.0 (−5.4 to 2.2)<0.001
FVC, % predicted
−0.3 (−6.0 to 5.7)
0.567
−1.4 (−7.1 to 4.6)
0.034

Definition of abbreviations: CRP = C-reactive protein; SGRQ = St. George's Respiratory Questionnaire; SP-D = surfactant protein D.

Data are shown as median and interquartile range. A negative number denotes a decrease in level/scores during the phase; whereas a positive number denotes an increase.

*P values are derived from Wilcoxon signed rank test.

Visit 3 (Withdrawal Phase)

Withdrawal of fluticasone for 1 month led to the following changes: the subjects' CRP changed by 0.0 (−1.3 to 1.3) mg/L (P = 0.829); IL-6 changed by −0.1 (−0.6 to 0.6) pg/ml (P = 0.728); SP-D changed by 5.6 (−4.5 to 20.1) ng/ml (P < 0.001); FEV1 changed by −1.0 (−5.4 to 2.2) % predicted (P < 0.001); and total SGRQ changed by 2.6 (−2.3 to 8.1) units (P < 0.001). The findings from the run-in and withdrawal phases are summarized in Table 2.

Visit 4 (Randomized Controlled Trial Phase)

Compliance with drugs was estimated by determining the dose that remained in the dispensed Diskus at the final visit. Sixty-nine percent of the study participants in the placebo, 80% in the fluticasone, and 76% in the combination groups demonstrated 85% or greater compliance with the assigned treatment drug (P = 0.461). The clinical characteristics of the study subjects at the time of randomization are summarized in Table 3. The changes in biomarkers, health status, and lung function between visits 3 and 4 are summarized in Table 4. Neither fluticasone nor the combination of fluticasone/salmeterol had any significant effect on CRP (primary endpoint) or IL-6 (secondary endpoint) levels. There was, however, a significant reduction in SP-D levels with fluticasone and fluticasone/salmeterol compared with placebo (P = 0.002). The SGRQ also improved significantly in both the fluticasone and the fluticasone/salmeterol groups compared with placebo, driven mostly by improvements in the symptom scores. There were no significant differences between the fluticasone and fluticasone/salmeterol groups in any of these parameters. FEV1 improved significantly in the fluticasone/salmeterol group compared with placebo. Changes in the circulating SP-D levels were related to changes in SGRQ scores between visits 3 and 4 (Figure 2). Subjects with the largest reduction in the circulating SP-D levels experienced the biggest improvements in health status as measured by the total SGRQ. Similarly, there was a significant relationship between circulating SP-D and changes in FEV1 between visits 3 and 4 (Figure 3). Subjects with the largest reduction in SP-D levels experienced the biggest improvements in FEV1. CRP changes were also associated with changes in total SGRQ scores (P < 0.001) but not with changes in FEV1 (P = 0.339). There was no significant relationship between changes in IL-6 and total SGRQ (P = 0.847) or FEV1 (P = 0.184).

TABLE 3. CHARACTERISTICS OF SUBJECTS AT THE TIME OF RANDOMIZATION




Placebo (n = 45)

Fluticasone (n = 87)

Fluticasone/Salmeterol (n = 92)

P Value
Age, yr66.8 ± 9.870.2 ± 9.069.6 ± 9.30.138
Men, %64.464.460.90.866
BMI, kg/m226.0 ± 5.627.8 ± 5.427.8 ± 6.20.166
Current smoker, %33.327.630.40.784
Pack-years*56.3 (40.0–91.0)63.0 (50.0–75.8)56.5 (39.0–73.7)0.156
FEV1, L1.38 ± 0.541.42 ± 0.531.33 ± 0.620.544
FEV1, % predicted47.0 ± 16.149.2 ± 15.345.8 ± 16.40.358
FVC, L2.85 ± 0.952.80 ± 0.692.80 ± 0.940.938
FVC, % predicted75.1 ± 18.274.2 ± 13.474.3 ± 17.90.958
Inhaled corticosteroids, %7164710.537
Combination therapy, %6253620.347
Statins, %2220240.858
CRP*, mg/L3.98 (1.56–7.82)2.73 (1.65–5.56)2.88 (1.07–7.53)0.511
IL-6*, pg/ml2.52 (1.67–4.37)2.21 (1.51–2.62)2.37 (1.56–3.50)0.598
SP-D*, ng/ml116.6 (90.6–147.2)107.9 (80.8–141.7)118.6 (84.4–161.1)0.315
SGRQ
 Total score43.6 ± 16.039.7 ± 15.442.4 ± 18.80.384
 Symptoms score56.7 ± 19.551.4 ± 24.050.8 ± 22.30.318
 Activity score61.5 ± 20.858.0 ± 19.060.3 ± 25.20.646
 Impacts score
29.3 ± 16.8
25.5 ± 14.9
29.4 ± 19.2
0.257

For definition of abbreviations, see Table 1.

Data are shown as mean ± SD, unless indicated otherwise. Continuous variables were compared using analysis of variance and dichotomous variables were compared using a χ2 test.

*Nonnormally distributed variables are shown as median (interquartile range); P value is derived from Kruskal-Wallis Test.

Medication taken at the time of enrollment. Combination therapy means combination of corticosteroid and a long-acting bronchodilator.

TABLE 4. CHANGES IN CIRCULATING BIOMARKERS, HEALTH STATUS, AND LUNG FUNCTION OF SUBJECTS OVER 1 MONTH ACCORDING TO RANDOMIZATION ASSIGNMENT




Placebo (n = 39)

Fluticasone (n = 85)

Fluticasone/Salmeterol (n = 88)

P Value*
CRP, mg/L−0.145 (−1.923 to 1.732)−0.168 (−1.385 to 0.691)0.074 (−1.205 to 2.674)0.537
IL-6, pg/ml−0.2 (−1.3 to 0.5)0.1 (−0.6 to 0.9)0.2 (−0.5 to 1.1)0.120
SP-D, ng/ml−1.9 (−9.8 to 15.2)−7.3 (−22.8 to -1.1)−12.3 (−28.4 to 0.4)0.002
SGRQ
 Total score1.5 (−4.5 to 6.1)−3.6 (−9.2 to 2.4)−2.4 (−7.9 to 3.4)0.022§
 Symptoms score1.5 (−6.9 to 9.8)−7.3 (−18.6 to 4.6)−3.1 (−15.4 to 5.8)0.037
 Activity score0.0 (−5.9 to 6.1)0.0 (−12.1 to 5.9)0.0 (−6.7 to 5.6)0.257
 Impacts score0.0 (−6.6 to 6.7)−2.0 (−8.1 to 3.2)−2.0 (−7.8 to 3.7)0.182
FEV1, % predicted1.0 (−3.9 to 3.9)1.6 (−1.1 to 5.9)3.8 (0.0 to 6.8)0.018
FVC, % predicted
2.3 (−4.7 to 4.8)
1.1 (−3.9 to 7.5)
1.9 (−1.5 to 6.8)
0.718

For definition of abbreviations, see Table 2.

Data are shown as median and interquartile range. A negative number denotes a decrease in level/scores with treatment, whereas a positive number denotes an increase.

*P values are derived from Kruskal-Wallis Test and the multiple Behrens-Fisher Test.

P = 0.016 for the comparison between placebo and fluticasone corrected for multiple comparisons.

P = 0.002 for the comparison between placebo and fluticasone/salmeterol corrected for multiple comparisons.

§P = 0.011 for the comparison between placebo and fluticasone corrected for multiple comparisons.

P = 0.001 for the comparison between placebo and fluticasone corrected for multiple comparisons.

P = 0.027 for the comparison between placebo and fluticasone/salmeterol corrected for multiple comparisons.

Exacerbation and Dropouts

There were significantly more exacerbations during the withdrawal than in the run-in phase. Moreover, subjects who received placebo Diskus experienced more exacerbations and were more likely to drop out compared with subjects who received fluticasone or fluticasone/salmeterol (see Table 5). All dropouts occurred because of worsening of respiratory symptoms related to the participant's COPD. There were no significant differences in exacerbations or dropouts between the fluticasone and fluticasone/salmeterol groups.

TABLE 5. EXACERBATION AND DROPOUTS DURING EACH PHASE OF THE STUDY






Randomized Treatment

Run-in (n = 289)
Withdrawal (n = 260)
P Value
Placebo (n = 45)
FP (n = 87)
FP/SALM (n = 92)
P Value
Exacerbations26 (9.0)39 (15.0)0.0307 (15.6)4 (4.6)5 (5.4)0.048*
Dropouts
29 (10.0)
36 (13.9)
0.168
6 (7.1)
2 (1.2)
4 (2.2)
0.039

Definition of abbreviations: FP = fluticasone; SALM = salmeterol.

Data are shown as number (percentage). Run in phase is from visit 1 to visit 2; withdrawal phase is from visit 2 to visit 3; active treatment phase is from visit 3 to visit 4.

*Fluticasone vs. placebo, P = 0.045; fluticasone/salmeterol vs. placebo, P = 0.060; fluticasone vs. fluticasone/salmeterol, P = 1.000.

Fluticasone vs. placebo, P = 0.019; fluticasone/salmeterol vs. placebo, P = 0.080; fluticasone vs. fluticasone/salmeterol, P = 0.683. Fisher's exact test was used for all subgroup comparisons.

Other Adverse Events

During the active treatment phase, 9% in the placebo, 6% in the fluticasone, and 10% in the combination arm complained of lower respiratory tract symptoms defined as cough and/or dyspnea (which did not result in dropping out or any additional treatment) (P = 0.620). Upper respiratory tract complaints defined as rhinorrhea, nasal congestion, and/or headache were reported in 4% of placebo-, 4% of fluticasone-, and 4% of the combination-treated groups (P = 0.908). There were no reported cases of pneumonia.

The present study is a novel multicenter clinical trial designed specifically to evaluate the effects of inhaled corticosteroids and combination therapy on systemic biomarkers of inflammation. With respect to the primary endpoint, inhaled fluticasone with or without salmeterol did not significantly change CRP levels in patients with stable COPD. These medications also failed to significantly alter serum IL-6 levels. However, they significantly reduced circulating SP-D levels and improved health status and lung function over a 4-week period. Withdrawal of fluticasone, conversely, increased SP-D levels, worsened health status, and reduced lung function in patients with moderate to severe COPD. These data suggest that fluticasone-based therapy reduces circulating lung-specific but not general biomarkers of systemic inflammation. Interestingly, the reductions in SP-D levels were associated with improved health status (especially dyspnea) and lung function, supporting the notion that lung inflammation plays an important role in health outcomes of patients with COPD.

Dissimilar to our previous report (11), in the present study we did not find a significant impact of fluticasone or combination product on CRP or IL-6 levels. Several explanations exist. First, the previous study evaluated a small number of patients, which may have caused a type 1 statistical error. Second, the previous cohort had milder lung function impairment. The average FEV1 was approximately 60% of predicted, whereas in the present study the average FEV1 was less than 50% of predicted. Lung function may modify the systemic action and absorption of inhaled corticosteroids (21). Third, there were fewer current smokers in the previous than in the present study. The clinical effects of corticosteroids may be modified by smoking status of patients; corticosteroids appear to be less effective in current than in former smokers (22). Fourth, a larger percentage of patients had been taking an inhaled corticosteroid long term before enrollment into this study than in the previous study and this treatment could have modified some of the inflammatory processes in the lungs.

The secondary finding that inhaled fluticasone with or without salmeterol significantly reduced SP-D levels may be of relevance in stable COPD. SP-D was chosen as an endpoint for several reasons. SP-D is a large, multimeric, collagenous glycoprotein weighing approximately 43 kD that plays an important role in innate immunity and in host defense responses against inhaled microorganisms and particles (23). SP-D also has a major function in regulating surfactant homeostasis in the lungs by modulating surfactant ultrastructure and promoting reuptake of surfactant by type II pneumocytes (24). SP-D is produced mainly by type II pneumocytes in the lungs, although other cells, such as Clara cells, endothelial cells, and glandular cells in the gastrointestinal tract, can produce trace amounts of SP-D (23). Acute lung injury in general increases both lung and serum SP-D levels. Cigarette smoking, on the other hand, induces a rise in the serum levels (25) but a fall in the bronchoalveolar lavage concentrations (26). Interestingly, mice exposed to cigarette smoke demonstrate increased expression of SP-D in the lungs at both the mRNA and protein level (27). Thus, the reduced bronchoalveolar lavage expression related to smoking is likely caused by leakage of SP-D from the lungs into the systemic circulation.

Within the pulmonary system, SP-D is generally beneficial in protecting the lungs from oxidant, inflammatory, and infectious stress (28). However, systemic expression of SP-D may be harmful (29). Overexpression of SP-D in the systemic circulation reduces high-density lipoprotein cholesterol levels and increases the risk of atherosclerosis (29). SP-D deficiency, on the other hand, protects mice against atherosclerosis (29). In human conditions, elevated levels of SP-D in the systemic circulation are associated with poor clinical outcomes in a variety of different settings. In acute respiratory distress syndrome of adults requiring mechanical ventilation, for example, elevated plasma SP-D levels are associated with increased risk of multiorgan failure, ventilator dependence, and even mortality (16). SP-D levels have also been noted to be elevated in other conditions such as allergic bronchopulmonary aspergillosis, community-acquired pneumonia, and interstitial lung diseases, and in these conditions, elevated SP-D levels are associated with disease severity and poor health status in these conditions (3032). In idiopathic pulmonary fibrosis, circulating SP-D levels predict long-term survival of these patients and changes in the serum value track clinical responses to therapy (33). Elevated serum SP-D levels have also been associated with increased risk of dementia and mortality in the general elderly population (34).

The mechanisms by which fluticasone and combination therapy reduce SP-D levels systemically are uncertain. In general, glucocorticoids up-regulate the expression of SP-D and other surfactant proteins in vivo and in vitro (35, 36). In theory, if anything, fluticasone and combination therapy should have caused an increase in the systemic expression of SP-D by increasing local production in the lungs. Altered production is therefore an unlikely explanation for the reduced SP-D expression related to corticosteroids. A more plausible explanation is that fluticasone and combination therapy reduced leakage of SP-D from the lung into the systemic compartments by attenuating lung inflammation and reducing epithelial and/or vascular permeability. Animal models have shown that lung injury and associated inflammation enhance spillage of SP-D molecules into the systemic circulation, causing increases in serum SP-D levels (37). Local application of corticosteroids, on the other hand, can reduce vascular leakage (38). However, because in the present study we did not measure lung expression of SP-D or quantified capillary leakage, we cannot draw clear inferences regarding the source of serum SP-D in patients with COPD or the mechanisms by which inhaled corticosteroids reduced serum expression of SP-D.

Whatever the mechanism, in the present study we found that the reduction in systemic levels of SP-D was associated with improved lung function and health status of patients with COPD, raising the possibility that SP-D may be a useful biomarker to track disease progression and clinical outcomes of patients with COPD. Because inflammation and lung function may be independent factors in the pathobiology of COPD, long-term studies powered on hard endpoints such as mortality and exacerbations are needed to validate new potential biomarkers in COPD (12).

Because our study did not include any subjects without COPD, the relationship between COPD and the inflammatory biomarkers is uncertain. Previous population-based studies have reported average CRP values between 1.5 to 2.5 mg/L in adults 40 years of age and older (13, 39, 40). The CRP values were generally higher in the present study, consistent with the notion that COPD is associated with low-grade systemic inflammation. Reported IL-6 and SP-D levels are more variable than those for CRP and there are no universally accepted reference values for these measurements in the general population. Previous large epidemiologic studies have reported average serum or plasma IL-6 levels of approximately 1.5 pg/ml (41, 42) and as high as 20 pg/ml (13). The average SP-D levels in the systemic circulation in subjects without overt disease have ranged from less than 50 ng/ml to nearly 1,500 ng/ml (34, 4345). The variability is likely due to a variety of factors, including differences in the clinical characteristics of the underlying populations and in the nature and performance of immunoassays used across the studies. SP-D levels are thus only comparable within, but not across, studies. In general, SP-D levels in the systemic circulation increase with age, current smoking status, and use of serum rather than plasma (44).

There were several limitations to the study. First, the duration of the study was relatively short. Thus, the long-term impact of fluticasone and combination therapy on systemic inflammation is uncertain. A relatively short follow-up period was chosen to minimize the effects of exacerbations, infections, and inflammatory insults, which are frequent occurrences in patients with moderate to severe COPD and can variably and unpredictably perturb systemic levels of CRP and other inflammatory biomarkers (46). Pinto-Plata and colleagues demonstrated a significant relationship between the (long-term) use of inhaled corticosteroids and reduced CRP levels in a group of patients with COPD (10). Thus, we cannot discount the possibility that long-term use of inhaled corticosteroids may reduce CRP levels in COPD. Second, we did not measure inflammatory biomarkers from lung samples due to a variety of technical and logistical constraints, including lack of standardization of sample collection, invasiveness of the procedure, and poor patient tolerability, that limit their application (47). Blood measurements, on the other hand, are more robust and are standardized. Notwithstanding the limitations of lung-based measurements, Barnes and colleagues have shown that combination therapy reduces various sputum and bronchial markers of inflammation in patients with moderate to severe COPD (48). Our findings extend these findings by demonstrating a significant impact on SP-D. Third, we did not ascertain the effects of these drugs on hard clinical outcomes such as hospitalization or mortality. Fourth, we did not evaluate the potential impact of bronchodilators on the inflammatory biomarkers. A recent study suggests that bronchodilators by themselves are unlikely to impact significantly on systemic markers of inflammation (49).

In summary, the present multicenter clinical trial failed to demonstrate any significant effect of inhaled fluticasone or combination therapy on systemic levels of CRP or IL-6, but they had a salutary effect on serum SP-D. The reductions in SP-D were associated with improved health status and lung function in patients with moderate to severe COPD. These data suggest that inhaled fluticasone and combination therapy reduce lung-specific but not some common biomarkers of systemic inflammation and raise the possibility of using SP-D and other lung-specific protein markers as an intermediate endpoint for future interventional studies in COPD.

The authors acknowledge and thank the site coordinators: Janet Baron (Royal University Hospital, Saskatoon); Georgina Lopez (St. Paul's Hospital, Vancouver); Anju Mainra (Lion's Gate Hospital, North Vancouver); Linda Hui, Maureen Sigurdson (Vancouver General Hospital, Vancouver); Kathy Duce (Lethbridge Regional Hospital, Lethbridge); Jill Edwards, Angie Depner (Links Clinic, Edmonton); Jennifer Barchard (Grey Nuns Community Hospital, Edmonton); Heidi Cheung (University of Alberta, Edmonton); Teena Rossitter (Wetaskiwin Lung Laboratory, Wetaskiwin); Amin Thawer, Diane Conley, Gladys Wolters (University of Calgary, Calgary). The authors also thank Mrs. Claire Gray (laboratory manager), Dr. Ted Watson (GSK), Ms. Jill Waddell (GSK), and Dr. Gerry Hagan (GSK Global) for their contributions to the project.

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Correspondence and requests for reprints should be addressed to S. F. Paul Man, M.D., Room 548, Burrard Building, St. Paul's Hospital, 1081 Burrard Street, Vancouver, BC, V6Z 1Y7 Canada. E-mail:

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