Letters to the Editor
Article first published online: 17 JAN 2003
Journal of General Internal Medicine
Volume 18, Issue 1, page 74, January 2003
How to Cite
Straus, S. E. and Mc Alisters, F. A. (2003), Letters to the Editor. Journal of General Internal Medicine, 18: 74. doi: 10.1046/j.1525-1497.2003.211192.x
- Issue published online: 17 JAN 2003
- Article first published online: 17 JAN 2003
Reply: —We appreciate Dr. Nardone's comments and his interest in our paper. We concur with Dr. Nardone that spirometry must be done in people with prolonged forced expiratory time.
As we stated in our article, forced expiratory time is not sufficient on its own to diagnose chronic obstructive pulmonary disease.1 Likelihood ratios greater than 10 and less than 0.10 are very useful in either ruling in or ruling out a target disorder.2 The pretest probability of disease becomes particularly important when likelihood ratios are between 0.10 and 10. In our previous paper, we stated that if the patient's pretest probability is 10%,3 and applying a likelihood ratio of 0.3, the posttest probability is sufficiently low that we would feel comfortable in ruling out the disease. However, if the pretest probability for a particular patient were higher, the posttest probability would be higher, such that we might not be comfortable ruling out the disease. Finally, the combined likelihood ratio of 59 was obtained from multiplying the adjusted likelihood ratios (adjusted for their nonindependence), not from the crude likelihood ratios. Therefore, they cannot be used directly to calculate sensitivity and specificity.—Sharon E. Straus, MD, Finlay A. Mc Alisters, On Behalf of the CARE-COAD Investigators.Toronto General Hospital, Toronto, Ontario, Canada.
- 3Evidence-based Medicine: How to Practise and Teach It. London: Harcourt Brace; 2000., , , , .