BMJ  2006;333:1123-1124 (25 November), doi:10.1136/bmj.39038.509167.1F

Letters

Statins and outcomes in patients with pneumonia

Not only healthy user bias

We read with interest the article on the use of statins for patients with pneumonia.¹ Although an important addition to the literature, several issues limit this article's usefulness.

The choice of an outcome measure combining in-hospital mortality and admission to intensive care is curious for a prospective study with such a rich clinical database. Previous research shows that 30 day mortality is largely pneumonia related,² and from our recent study,³ 33% of deaths were after discharge and before 30 days. A preferred way to examine the impact of statins on sepsis would be to examine sepsis-related outcomes (vasopressor use, incidence of severe sepsis, or mortality alone).

The findings that age >65 years, ischaemic heart disease, and using levofloxacin are protective, or that PSI ⁴ class III has an odds ratio of 2.45, have not been previously reported and seem implausible. Inclusion of younger subjects who are less often prescribed statins, and are at much lower risk for mortality, reduces the ability to see an effect. A specific list of variables entered into the final model would be informative to assess potential multicollinearity.

We also believe it is inappropriate to label the odds ratios as "potential harm" or "potential benefit" as all of the 95% confidence intervals include 1.0. These odds ratios and 95% confidence intervals show no association, not potential "harm" or "benefit."

Overall, the study suffers from faults in the study analyses, notably a failure to assess interactions and multicollinearity in the face of counterintuitive results, undermining the contention that previous findings may be attributable to healthy user bias. Future research needs to adjust for factors associated with healthy user bias, patient frailty, and other forms of potential confounding. Only well designed randomised controlled trials will be able to determine finally whether statins have a role in the management of serious infectious diseases.

¹ University of Texas Health Science Center at San Antonio, 7400 Merton Minter Boulevard (11C6), San Antonio, TX 78229, USA

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Competing interests: None declared.

References

1. Majumdar SR, McAlister FA, Eurich DT, Padwal RS, Marrie TJ. Statins and outcomes in patients admitted to hospital with community acquired pneumonia: population based prospective cohort study. BMJ 2006;333:999-1001. (11 November.)[Abstract/Free Full Text]
2. Mortensen EM, Coley CM, Singer DE, Marrie TJ, Obrosky DS, Kapoor WN, Causes of death for patients with community-acquired pneumonia: results from the Pneumonia Patient Outcomes Research Team cohort study. Arch Intern Med 2002;162(9):1059-64.[Abstract/Free Full Text]
3. Mortensen EM, Restrepo M, Anzueto A, Pugh J. The effect of prior statin use on 30-day mortality for patients hospitalized with community-acquired pneumonia. Resp Res 2005;6:82.
4. Fine MJ, Auble TE, Yealy DM, Hanusa BH, Weissfeld LA, Singer DE, A prediction rule to identify low-risk patients with community-acquired pneumonia. N Engl J Med 1997;336:243-50.[Abstract/Free Full Text]

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Relevant Article

Statins and outcomes in patients admitted to hospital with community acquired pneumonia: population based prospective cohort study

Sumit R Majumdar, Finlay A McAlister, Dean T Eurich, Raj S Padwal, and Thomas J Marrie
BMJ 2006 333: 999. [Abstract] [Full Text] [PDF]