Letters

Stable chronic obstructive pulmonary disease

BMJ 2000; 320 doi: https://doi.org/10.1136/bmj.320.7230.312 (Published 29 January 2000) Cite this as: BMJ 2000;320:312

Incomplete evidence based reviews may condemn by omission

  1. M C Steiner, research fellow (michael.steiner{at}glenfield-tr.trent.nhs.uk),
  2. S Singh, director of rehabilitation,
  3. M D L Morgan, consultant physician
  1. Glenfield Hospital, Leicester LE3 9QP
  2. Department of Medicine, University of Auckland, Auckland, New Zealand
  3. Department of Pulmonary Diseases, University Hospital Groningen, PO Box 30 001, 9700 RB Groningen, Netherlands

    EDITOR—The review by Kerstjens published in the BMJ on behalf of Clinical Evidenceclaims to be an evidence based account of treatment for stable chronic obstructive pulmonary disease.1 Unfortunately, the author restricted his analysis to drug treatments and therefore omitted non-pharmacological treatments, which may be of great benefit to patients with the disease.

    In particular, pulmonary rehabilitation provides benefits to patients in terms of exercise capacity and quality of life, outcomes that were clearly included in the aims of the review. The benefits of pulmonary rehabilitation have been validated in well designed and executed randomised controlled trials.2 3 Indeed,the clinical efficacy of rehabilitation is greater than that of many drug treatments.4 Evidence based guidelines for pulmonary rehabilitation have been published.5

    Provision of pulmonary rehabilitation in the United Kingdom lags behind that in the United States and the rest of Europe. Incomplete evidence based reviews such as this may worsen the situation by giving the impression that treatments not included in its analysis are of no benefit.

    References

    1. 1.
    2. 2.
    3. 3.
    4. 4.
    5. 5.

    Published correction for one of studies must be borne in mind

    1. Phillippa Poole, senior lecturer in medicine (p.poole{at}auckland.ac.nz),
    2. Peter Black, senior lecturer in medicine
    1. Glenfield Hospital, Leicester LE3 9QP
    2. Department of Medicine, University of Auckland, Auckland, New Zealand
    3. Department of Pulmonary Diseases, University Hospital Groningen, PO Box 30 001, 9700 RB Groningen, Netherlands

      EDITOR—Kerstjens's clinical review on stable chronic obstructive pulmonary disease1 cited our systematic review on the effect of mucolytics on exacerbations of chronic bronchitis.2 As noted in the article, we found that treatment with mucolytics led to a significant reduction in the frequency of exacerbations and to a reduction in the days of disability. There was, however, an error in our review, as published in the Cochrane Library, which we would like to point out. As stated in the article, the effect size for the change in forced expiratory volume in one second was 57 ml; for the vital capacity it was 40 ml, but the change was in the opposite direction. In other words, treatment with mucolytics led to a small increase in lung function, not a decrease.

      We think that this finding should be interpreted with caution because it was based on only three trials that reported forced expiratory volume in one second and four that reported vital capacity and there was considerable heterogeneity in the studies. Furthermore, these changes are small and fall within the coefficient of variation for spirometry. Nevertheless, on the basis of these studies we cannot conclude that mucolytics have a deleterious effect. This error will be corrected in the next update of the Cochrane Library.

      We would also like to point out one other error in the article. It says that we did not find any effect on antibiotic use, but this is not the case. The review reported a significant difference in the number of days for which the patients were taking antibiotics. The weighted mean difference was a reduction in 0.68 days of treatment with antibiotics for each month of treatment with mucolytics (95% confidence interval−0.71 to −0.64,P<0.001).

      Our review was not able to address the effect of mucolytics on long term decline in lung function, but we await with interest studies that will do this.

      References

      1. 1.
      2. 2.

      Author's reply

      1. Huib A M Kerstjens, pulmonary physician (H.A.M.Kerstjens{at}int.azg.nl)
      1. Glenfield Hospital, Leicester LE3 9QP
      2. Department of Medicine, University of Auckland, Auckland, New Zealand
      3. Department of Pulmonary Diseases, University Hospital Groningen, PO Box 30 001, 9700 RB Groningen, Netherlands

        EDITOR—The review in the BMJis taken from issue 1 of Clinical Evidence,a new information resource for clinicians.1 Steiner et al have noticed correctly that only maintenance drugs were covered, and not rehabilitation. Unfortunately, the first line of the review in Clinical Evidence,which underlined the fact that only maintenance drug treatment was covered,was not included in the review in the BMJ.

        Many other interventions were not covered—among them the most important one in the disease (smoking cessation) but also nutrition. Additionally, interventions during acute exacerbations were not discussed. Clearly no inference about (lack of) benefit should be drawn from topics not covered in the review. The compendium will be updated and expanded every six months, and rehabilitation will certainly need to be added, together with several other topics.

        I gratefully acknowledge the corrections of errors by Poole and Black. As stated in the review, the effect of N—acetylcysteine on long term decline in lung function is currently the subject of a large European multicentre study, and the results are eagerly awaited.

        References

        1. 1.
        View Abstract

        Log in

        Log in through your institution

        Subscribe

        * For online subscription