Health Evidence Bulletins - Wales
Team Leader: Dr Michael Burr Date of completion: 5/3/98


The original Protocols for Investment in Health Gain were written in the early 1990s to suggest areas where the introduction, or more widespread use, of certain practices could lead to worthwhile improvements in health for the people of Wales. The documents also highlighted current practices which were of questionable value. This revision has been prepared by reviewing the earlier Protocol for Investment in Health Gain: Respiratory Diseases(1) to provide some clear, updated statements with a precise indication of the strength of the evidence and its sources for each statement; and to introduce new statements covering subjects of important current interest.

In keeping with the original Protocols, these revised documents are designed to assist Health Authorities in developing local strategies and in purchasing high quality health care. It is anticipated, however, that they will be of value to all health professionals in keeping abreast of the huge and increasing body of medical literature and can provide an agenda for future action in a wide variety of settings. It should be stressed that the Protocols will act as a supplement to, not a substitute for, clinical skills and experience.

The statements represent a systematic summary of the evidence in this area found through a formal literature search across a wide range of sources(2). The evidence has been critically appraised using internationally accepted methods(2), compiled into this document under the direction of a public health physician, and reviewed by a multidisciplinary team who are directly involved in patient care(3). In addition to this document, the information will be available electronically, via the NHS Cymruweb. Information on the methodology adopted (including a copy of the documentation), the formats in which the document is issued and details of other publications in the series, is available on request(4).

The convention used in this document to indicate the type of evidence is(5):

‘Type I evidence’ - at least one good systematic review
(including at least one randomised controlled trial).
‘Type II evidence’ - at least one good randomised controlled trial
‘Type III evidence’ - well designed interventional studies without randomisation
‘Type IV evidence’ - well designed observational studies
‘Type V evidence’ - expert opinion; influential reports and studies

The health gain notation (used to indicate the potential benefit to health) is(6):


‘beneficial’ - effectiveness clearly demonstrated (1)
‘likely to be beneficial’ - effectiveness not so firmly established (2)
‘trade-off between beneficial and adverse effects’ - effects weighed according to individual circumstances(3)
‘unknown’ - insufficient/inadequate for recommendation (4)
‘unlikely to be beneficial’ - ineffectiveness is not as clearly demonstrated as for 6 (5)
‘likely to be ineffective or harmful’ - ineffectiveness or harm clearly demonstrated (6)

It should be stressed that these gradings, while aiming to be impartial, represent only the best advice of the professionals involved in preparing the Bulletin. Although the statements are deliberately brief, statistically significant quantitative information has been provided where possible. This is usually given as Number Needed to Treat (NNT), Odds Ratio (OR) or % change, in keeping with the original source of the information(7). Cost-benefit issues are not considered.

The Respiratory Diseases Bulletin

The respiratory diseases are the conditions that affect the nose, throat, larynx, bronchial tree and lungs. They constitute the commonest reason for consulting a general practitioner(8) and cause large numbers of deaths(9), so that it is particularly important to ensure that they are treated effectively. Active(10) and passive smoking(11) are major factors in the causation and aggravation of respiratory diseases. Air pollution may also be influential(12).

This Bulletin deals with the management of the commoner respiratory diseases. It does not include cancers of the respiratory tract, which will be considered within the Cancers Bulletin(13). Because respiratory diseases are so common, a large and growing body of evidence exists about the effectiveness of different forms of treatment. The purpose of this document is to review the ways in which these diseases are managed, in terms of the quality of the evidence for believing that any given treatment is effective.

Systematic reviews and meta-analyses were used where they exist; otherwise, individual randomised controlled trials are cited, with the attendant danger of selective bias in view of the large number of trials on some topics. Although it is neither necessary nor feasible to cite every piece of evidence, readers who know of important studies that have been overlooked are asked to notify the team leader about them(14).


Randomised trials compare the effects of different treatments (or of a given treatment versus no treatment) in groups of patients which are assumed to be fairly homogeneous, and the conclusions relate to the effects in the whole groups (or definable subgroups) without distinguishing more subtle differences between individuals. It may well be the case that a given treatment is more appropriate for one patient than for another within the same grouping. The statements made in this Bulletin do not override the exercise of clinical judgement, which should be the ultimate basis on which the treatment of an individual patient is determined

Other bulletins in the series address the following subjects:

This project is funded by the Wales Office of Research and Development for Health and Social Care


Dr Michael Burr, Team Leader, Respiratory Diseases Bulletin: March 1998

  1. Welsh Health Planning Forum.  Cardif: Welsh Office NHS Directorate, February 1992
  2. Barker J, Weightman AL and Lancaster J.  Project for the Enhancement of the Weslh Protocols for Investment in Health Gain: Project Methodology 2. Cardiff: Duthie Library UWCM, 1997
  3. See Contributors
  4. Contact: Protocol Enhancement Project Office, Duthie Library, UWCM, Heath Park, Cardiff CF4 4XN
  5. This table is adapted from the Bandolier system (derived from work at McMaster University, Canada) using the NHS Centre for Reviews and Dissemination criteria for a systematic review.  See ref.3 or and the Database of Abstracts of Reviews of Effectiveness (DARE) in the Cochrane Library.
  6. This Notation is modified from the tables used in Enkin M, Keirse MJNC, Renfrew m and Neilson J.  A guide to effective care in pregnancy and childbirth. 2nd ed.  Oxford: Oxford University Press, 1995 pp. 389-390
  7. Number Needed to Treat (NNT) = The number of patients to be treated to be sure of gaining one positive outcome;
  8. Odds Ratio (OR): If equal to 1, then the effects of the treatment are no different from those of the control treatment.  If the OR is greater (or less) than 1, then the effects of the treatment are more (or less) than those of the control treatment.  Note that the effect being measured may be adverse or desirable.
  9. McCormick A, Fleming D, Charlton J; Office of Population Censuses and Surveys.  Morbidity statistics from general practice.  Fourth national study 1991-1992. Series MB5 No.3. London:  HMSO, 1995 pp.66-67, 72, 74
  10. Office for National Statistics.  1995 Mortality Statistics: Cause.   England and Wales.  Series DH2 No.22. London: HMSO, 1997
  11. Peto R, Lopez AD, Boreham J, Thun M, Heath C.Jr; Imperial Cancer Research Fund: World Health Organisation.  Mortality from smoking in developed countries 1950-2000. Oxford: Oxford University Press, 1994. pp.528-529
  12. DiFranza JR, Lew RA.  Morbidity and mortality in children associated with the use of tobacco products by other people.  Pediatrics.  1996; 97(4): 560-568
  13. Protocol Enhancement Project.  Cancers Bulletin.  Due for publication in 1998.
  14. Contact Dr Michael Burr via the Protocol Enhancement Project Office (see ref.4)

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