Letters

Ratio of inhaled corticosteroid to bronchodilator as indicator of quality of asthma prescribing

BMJ 1997; 314 doi: https://doi.org/10.1136/bmj.314.7081.680a (Published 01 March 1997) Cite this as: BMJ 1997;314:680

Authors discuss a result that was not shown

  1. Sarah J Roberts, Lecturer in medical statisticsa
  1. a Wolfson Unit of Clinical Pharmacology, University of Newcastle, Newcastle upon Tyne NE2 4HH
  2. b Department of Child Health, Derriford Hospital, Plymouth PL6 8DH
  3. c Department of Medicine, University Hospital of Wales, Cardiff CF4 4XW
  4. d Department of General Practice and Primary Care, St Bartholomew's and the Royal London School of Medicine and Dentistry, London EC1M 6BQ
  5. e Department of Medical Statistics, Royal Postgraduate Medical School, London W12 0NN
  6. f General Practice and Primary Health Care, Imperial College School of Medicine at St Mary's, London W2 1PG
  7. g Department of Epidemiology and Medical Statistics, Queen Mary and Westfield College, London
  8. h Industrial and Community Health Research Centre, School of Postgraduate Medicine, Keele University, North Staffordshire Medical Institute, Stoke on Trent ST4 7NY
  9. i Department of Medicines Management, Keele University, Keele, Staffordshire ST5 5BG

    Editor–The paper by Michael Shelley and colleagues on the ratio of inhaled corticosteroids to bronchodilators prescribed shows an innovation in research reporting–discussion of a result that has not been shown.1 Having failed to confirm any association between this prescribing ratio and rates of admission to hospital for asthma within either a group of deprived practices or a group of more affluent practices, the authors then discuss the reasons for inconsistencies between these two non-associations and the role that deprivation may have.

    No associations are visibly evident in their scatterplots of the data, and I suspect that other readers would also have had difficulty in deciding which of the plots related to the non-significant positive correlation (Spearman's r=0.038, P=0.792) and which to the negative correlation (rs=-0.218, P=0.136). No hypothesis of a difference between these two correlations was tested.

    Nevertheless, I agree with the authors that the ratio of inhaled corticosteroids to bronchodilators prescribed may not be a good indicator of the quality of treatment of asthma. As with all ratios and percentages, it gives no indication of the absolute quantities concerned. Small ratios could derive from good prescribing of inhaled steroids for asthma and overprescribing of bronchodilators for asthma, chronic obstructive pulmonary disease, or chronic bronchitis; alternatively, small ratios could derive from reasonable prescribing of bronchodilators with a deficiency in prescribing of inhaled steroids to asthmatic patients. The quality of prescribing in asthma might possibly be indicated by the quantity of inhaled steroids relative to the number of asthmatic patients. There is no evidence, however, that the quantity of bronchodilators prescribed is a good surrogate measure for the number of patients with asthma in a practice, especially as asthma is far less strongly related to age than many of the other respiratory conditions for which bronchodilators are additionally …

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