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Exhaled carbon monoxide in asthmatics: a meta-analysis.

Zhang J, Yao X, Yu R, Bai J, Sun Y, Huang M, Adcock IM, Barnes PJ - Respir. Res. (2010)

Bottom Line: Exhaled carbon monoxide (eCO) measurement is cheap and has been proposed to reflect airway inflammation and oxidative stress but current data are conflicting.A systematic search for English language articles published between 1997 and 2009 was performed using Medline, Embase and Cochrane databases.Data were independently extracted by two investigators and analyzed to generate weighted mean differences using either a fixed or random effects meta-analysis depending upon the degree of heterogeneity. 18 studies were included in the meta-analysis.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Respiratory Disease, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China.

ABSTRACT

Background: The non-invasive assessment of airway inflammation is potentially advantageous in asthma management. Exhaled carbon monoxide (eCO) measurement is cheap and has been proposed to reflect airway inflammation and oxidative stress but current data are conflicting. The purpose of this meta-analysis is to determine whether eCO is elevated in asthmatics, is regulated by steroid treatment and reflects disease severity and control.

Methods: A systematic search for English language articles published between 1997 and 2009 was performed using Medline, Embase and Cochrane databases. Observational studies comparing eCO in non-smoking asthmatics and healthy subjects or asthmatics before and after steroid treatment were included. Data were independently extracted by two investigators and analyzed to generate weighted mean differences using either a fixed or random effects meta-analysis depending upon the degree of heterogeneity.

Results: 18 studies were included in the meta-analysis. The eCO level was significantly higher in asthmatics as compared to healthy subjects and in intermittent asthma as compared to persistent asthma. However, eCO could not distinguish between steroid-treated asthmatics and steroid-free patients nor separate controlled and partly-controlled asthma from uncontrolled asthma in cross-sectional studies. In contrast, eCO was significantly reduced following a course of corticosteroid treatment.

Conclusions: eCO is elevated in asthmatics but levels only partially reflect disease severity and control. eCO might be a potentially useful non-invasive biomarker of airway inflammation and oxidative stress in nonsmoking asthmatics.

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Related in: MedlinePlus

eCO levels in steroid-free and steroid-treated asthmatics. The WMD of eCO levels between steroid-free asthmatics and healthy subjects is 1.39 ppm (95%CI: 0.82 to 1.95) using the random effects model. Test for heterogeneity I2 = 91%. The WMD of eCO levels between steroid-treated asthmatics and healthy adults is 0.79 ppm (95%CI: 0.35 to 1.23) using the random effects model. Test for heterogeneity I2 = 84%. SD: standard deviation; IV: inverse variance; CI: confidence interval; WMD: weighted mean difference; eCO: exhaled carbon monoxide.
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Figure 5: eCO levels in steroid-free and steroid-treated asthmatics. The WMD of eCO levels between steroid-free asthmatics and healthy subjects is 1.39 ppm (95%CI: 0.82 to 1.95) using the random effects model. Test for heterogeneity I2 = 91%. The WMD of eCO levels between steroid-treated asthmatics and healthy adults is 0.79 ppm (95%CI: 0.35 to 1.23) using the random effects model. Test for heterogeneity I2 = 84%. SD: standard deviation; IV: inverse variance; CI: confidence interval; WMD: weighted mean difference; eCO: exhaled carbon monoxide.

Mentions: 13 articles mentioned steroid-free asthmatics (defined as either steroid naïve or not receiving regular inhaled or systemic corticosteroids and treated by on-demand β2-agonist), and 8 articles mentioned steroid-treated asthmatics (defined as current use of inhaled or systemic corticosteroids irrespective of β2-agonist or montelukast use). The WMD of eCO was 1.39 ppm (95%CI 0.82 to 1.95; I2 = 91%; Random effects model) between steroid-free asthmatics and healthy subjects, and 0.79 ppm (95%CI 0.35 to 1.23; I2 = 84%; Random effects model) between steroid-treated asthmatics and healthy subjects. Both steroid-free and steroid-treated asthmatics had significantly higher eCO levels than healthy subjects. Steroid-treated asthmatic patients had lower eCO levels compared to steroid-free asthmatic patients (0.79 ppm vs 1.39 ppm) but this failed to reach statistical significance. (Figure 5)


Exhaled carbon monoxide in asthmatics: a meta-analysis.

Zhang J, Yao X, Yu R, Bai J, Sun Y, Huang M, Adcock IM, Barnes PJ - Respir. Res. (2010)

eCO levels in steroid-free and steroid-treated asthmatics. The WMD of eCO levels between steroid-free asthmatics and healthy subjects is 1.39 ppm (95%CI: 0.82 to 1.95) using the random effects model. Test for heterogeneity I2 = 91%. The WMD of eCO levels between steroid-treated asthmatics and healthy adults is 0.79 ppm (95%CI: 0.35 to 1.23) using the random effects model. Test for heterogeneity I2 = 84%. SD: standard deviation; IV: inverse variance; CI: confidence interval; WMD: weighted mean difference; eCO: exhaled carbon monoxide.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2874770&req=5

Figure 5: eCO levels in steroid-free and steroid-treated asthmatics. The WMD of eCO levels between steroid-free asthmatics and healthy subjects is 1.39 ppm (95%CI: 0.82 to 1.95) using the random effects model. Test for heterogeneity I2 = 91%. The WMD of eCO levels between steroid-treated asthmatics and healthy adults is 0.79 ppm (95%CI: 0.35 to 1.23) using the random effects model. Test for heterogeneity I2 = 84%. SD: standard deviation; IV: inverse variance; CI: confidence interval; WMD: weighted mean difference; eCO: exhaled carbon monoxide.
Mentions: 13 articles mentioned steroid-free asthmatics (defined as either steroid naïve or not receiving regular inhaled or systemic corticosteroids and treated by on-demand β2-agonist), and 8 articles mentioned steroid-treated asthmatics (defined as current use of inhaled or systemic corticosteroids irrespective of β2-agonist or montelukast use). The WMD of eCO was 1.39 ppm (95%CI 0.82 to 1.95; I2 = 91%; Random effects model) between steroid-free asthmatics and healthy subjects, and 0.79 ppm (95%CI 0.35 to 1.23; I2 = 84%; Random effects model) between steroid-treated asthmatics and healthy subjects. Both steroid-free and steroid-treated asthmatics had significantly higher eCO levels than healthy subjects. Steroid-treated asthmatic patients had lower eCO levels compared to steroid-free asthmatic patients (0.79 ppm vs 1.39 ppm) but this failed to reach statistical significance. (Figure 5)

Bottom Line: Exhaled carbon monoxide (eCO) measurement is cheap and has been proposed to reflect airway inflammation and oxidative stress but current data are conflicting.A systematic search for English language articles published between 1997 and 2009 was performed using Medline, Embase and Cochrane databases.Data were independently extracted by two investigators and analyzed to generate weighted mean differences using either a fixed or random effects meta-analysis depending upon the degree of heterogeneity. 18 studies were included in the meta-analysis.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Respiratory Disease, The First Affiliated Hospital of Nanjing Medical University, Nanjing, China.

ABSTRACT

Background: The non-invasive assessment of airway inflammation is potentially advantageous in asthma management. Exhaled carbon monoxide (eCO) measurement is cheap and has been proposed to reflect airway inflammation and oxidative stress but current data are conflicting. The purpose of this meta-analysis is to determine whether eCO is elevated in asthmatics, is regulated by steroid treatment and reflects disease severity and control.

Methods: A systematic search for English language articles published between 1997 and 2009 was performed using Medline, Embase and Cochrane databases. Observational studies comparing eCO in non-smoking asthmatics and healthy subjects or asthmatics before and after steroid treatment were included. Data were independently extracted by two investigators and analyzed to generate weighted mean differences using either a fixed or random effects meta-analysis depending upon the degree of heterogeneity.

Results: 18 studies were included in the meta-analysis. The eCO level was significantly higher in asthmatics as compared to healthy subjects and in intermittent asthma as compared to persistent asthma. However, eCO could not distinguish between steroid-treated asthmatics and steroid-free patients nor separate controlled and partly-controlled asthma from uncontrolled asthma in cross-sectional studies. In contrast, eCO was significantly reduced following a course of corticosteroid treatment.

Conclusions: eCO is elevated in asthmatics but levels only partially reflect disease severity and control. eCO might be a potentially useful non-invasive biomarker of airway inflammation and oxidative stress in nonsmoking asthmatics.

Show MeSH
Related in: MedlinePlus