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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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eCO levels in different asthma control states. The WMD of eCO levels between controlled + partly controlled asthmatics and healthy subjects is 1.20 ppm (95%CI: 0.39 to 2.01) using the random effects model. Test for heterogeneity I2 = 91%. The WMD of eCO levels between uncontrolled asthmatics and healthy adults is 2.12 ppm (95%CI: 0.56 to 3.68) using the random effects model. Test for heterogeneity I2 = 95%. SD: standard deviation; IV: inverse variance; CI: confidence interval; WMD: weighted mean difference; eCO: exhaled carbon monoxide.
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Figure 8: eCO levels in different asthma control states. The WMD of eCO levels between controlled + partly controlled asthmatics and healthy subjects is 1.20 ppm (95%CI: 0.39 to 2.01) using the random effects model. Test for heterogeneity I2 = 91%. The WMD of eCO levels between uncontrolled asthmatics and healthy adults is 2.12 ppm (95%CI: 0.56 to 3.68) using the random effects model. Test for heterogeneity I2 = 95%. SD: standard deviation; IV: inverse variance; CI: confidence interval; WMD: weighted mean difference; eCO: exhaled carbon monoxide.

Mentions: We attempted to classify asthma control status into 3 categories: controlled, partly controlled and uncontrolled [1]. However, some studies did not provide enough information to distinguish between controlled and partly controlled disease. Thus, we divided subjects into 2 groups: controlled + partly controlled group (6 articles) and uncontrolled group (3 articles). The WMD of eCO was 1.20 ppm (95%CI 0.39 to 2.01; I2 = 91%; Random effects model) between controlled + partly controlled asthmatics and healthy subjects, and 2.12 ppm (95%CI 0.56 to 3.68; I2 = 95%; Random effects model) between uncontrolled asthmatics and healthy subjects. Both controlled + partly controlled asthma and uncontrolled asthma showed significantly higher eCO levels as compared to healthy subjects. There was no statistical difference in eCO levels between controlled + partly controlled and uncontrolled asthma. (Figure 8)


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 different asthma control states. The WMD of eCO levels between controlled + partly controlled asthmatics and healthy subjects is 1.20 ppm (95%CI: 0.39 to 2.01) using the random effects model. Test for heterogeneity I2 = 91%. The WMD of eCO levels between uncontrolled asthmatics and healthy adults is 2.12 ppm (95%CI: 0.56 to 3.68) using the random effects model. Test for heterogeneity I2 = 95%. 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 8: eCO levels in different asthma control states. The WMD of eCO levels between controlled + partly controlled asthmatics and healthy subjects is 1.20 ppm (95%CI: 0.39 to 2.01) using the random effects model. Test for heterogeneity I2 = 91%. The WMD of eCO levels between uncontrolled asthmatics and healthy adults is 2.12 ppm (95%CI: 0.56 to 3.68) using the random effects model. Test for heterogeneity I2 = 95%. SD: standard deviation; IV: inverse variance; CI: confidence interval; WMD: weighted mean difference; eCO: exhaled carbon monoxide.
Mentions: We attempted to classify asthma control status into 3 categories: controlled, partly controlled and uncontrolled [1]. However, some studies did not provide enough information to distinguish between controlled and partly controlled disease. Thus, we divided subjects into 2 groups: controlled + partly controlled group (6 articles) and uncontrolled group (3 articles). The WMD of eCO was 1.20 ppm (95%CI 0.39 to 2.01; I2 = 91%; Random effects model) between controlled + partly controlled asthmatics and healthy subjects, and 2.12 ppm (95%CI 0.56 to 3.68; I2 = 95%; Random effects model) between uncontrolled asthmatics and healthy subjects. Both controlled + partly controlled asthma and uncontrolled asthma showed significantly higher eCO levels as compared to healthy subjects. There was no statistical difference in eCO levels between controlled + partly controlled and uncontrolled asthma. (Figure 8)

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