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BMJ. 2007 December 15; 335(7632): 1225.
PMCID: PMC2137048
Prognostic Pessimism

Don’t group COPD and asthma

Suveer Singh, consultant in intensive care and respiratory medicine,1 Daffyd Lloyd, anaesthesia resident,1 Tasneem Katawala, anaesthesia resident,1 James Harris, anaesthesia resident,1 and Radha Sabharatnam, foundation year 11

We have concerns about the CAOS study’s interpretation of prognostic estimates by grouping chronic obstructive pulmonary disease (COPD) and asthma together1: this may underestimate the true discrepancy suggested.

Asthma and COPD are essentially different diseases, in terms of aetiology, clinical course of exacerbations, and responses to critical care interventions—for example, ventilatory management. Furthermore, the inhospital death rates for intubated patients are notably different, at 20-30% for COPD2 3 and about 10% for asthma.4

Both diseases have differing prognostic indicators of outcomes, which may have an important influence on intensive care clinicians’ judgments on whether to admit such patients.

We believe that patients with severe asthma are much less likely to be refused admission to intensive care or intubation than patients with severe exacerbations of COPD. Furthermore, perceptions of out of hospital survival for asthma are likely to be better than for COPD. We therefore speculate that the difference between predicted and actuarial survival of the CAOS cohort is likely to have been an underestimate of the prognostic pessimism in a COPD cohort.

Is it not this particular group who we are really concerned may be “missing out” on the services of intensive care units? We would welcome presentation of the data for COPD alone.


Competing interests: None declared.


1. Wildman MJ, Sanderson C, Groves J, Reeves BC, Ayres J, Harrison D, et al. Implications of prognostic pessimism in patients with chronic obstructive pulmonary disease (COPD) or asthma admitted to intensive care in the UK within the COPD and asthma outcome study (CAOS): multicentre observational cohort study. BMJ 2007;335:1132-4. (1 December.) [PMC free article] [PubMed]
2. Seneff MG, Wagner DP, Wagner RP, Zimmerman JE, Knaus WA. Hospital and 1-year survival of patients admitted to intensive care units with acute exacerbation of chronic obstructive pulmonary disease. JAMA 1995;274:1852-7. [PubMed]
3. Breen D, Churches T, Hawker F, Torzillo PJ. Acute respiratory failure secondary to chronic obstructive pulmonary disease treated in the intensive care unit: a long term follow up study. Thorax 2002;57:29-33. [PMC free article] [PubMed]
4. Gupta D, Keogh B, Chung KF, Ayres JG, Harrison DA, Goldfrad C, et al. Characteristics and outcome for admissions to adult, general critical care units with acute severe asthma: a secondary analysis of the ICNARC case mix programme database. Crit Care 2004;8:R112-21. [PMC free article] [PubMed]

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