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Ryan et al.,
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A model that gives individual estimates within a continuous range should be preferred to one that gives only four risk strata (0.3 percent, 3 percent, 33 percent, and 87 percent). Indeed, all tests used to assess the severity of illness in patients in the intensive care unit (the Acute Physiologic and Chronic Health Evaluation III and the Simplified Acute Physiologic Score II) provide probabilities within a continuous range. This allows one to evaluate models by calculating their discriminant power (the area under the receiver-operating-characteristic curve) and their calibration (goodness-of-fit test).2 Because these data are lacking in the study by Ryan et al., their model cannot be compared with other models proposed for use in patients with burn injuries, such as the one described by Smith et al.,3 which relies on the same variables and provides individual estimates of the probability of death within a continuous range.
Jean Edouard Rohan, M.D.
Cristina Esteban, M.D.
Philippe Loirat, M.D.
Hôpital Foch
92151 Suresnes, France
References
Thomas G. Hooyman, Ph.D.
Catholic Health Initiatives
Denver, CO 80202
To the Editor: The system for objectively estimating the probability of death from burn injuries is designed to help health care providers furnish initial information on mortality to patients and families, assist medical personnel with triage at injury scenes, and help researchers plan inclusion criteria for clinical trials in which mortality is a relevant end point. For these purposes, the method should be easy to use and applicable to all patients with burn injuries who require hospital treatment. Our goal was to develop a method based on a limited set of clinically apparent risk factors that could easily be determined. This method is not meant to replace severity scores that use continuous variables, such as the Acute Physiologic and Chronic Health Evaluation III index, or burn formulas1,2 that were developed for other purposes and have been found to be impractical in these settings.
Our study identified a population (patients over 60 years of age with a burn size of more than 40 percent of body-surface area and inhalation injury) with a high risk of death (87 percent), as noted by Dr. Hooyman. There were only a small number of patients in this group, resulting in the lower boundary of the 95 percent confidence interval (78 percent) noted by Dr. Rohan and colleagues. We think that this level of precision is adequate for the above-mentioned purposes, especially given the complex nature of decisions about whether to provide resuscitation in situations in which the risk of death is high.
The increased incidence of patients with burn injuries who had do-not-resuscitate orders between the period from 1975 to 1984 and the period from 1990 to 1994 coincides with the growing emphasis on patient autonomy. Documentation of advance directives became mandatory for Medicare reimbursement in 1991.
Medical futility remains undefined. Patients and surrogates can refuse life-prolonging treatment regardless of the prognosis. Only when doctors judge that treatment is futile and oppose requests for treatment does the issue of futility become relevant. A doctor's refusal to accede to requests for treatment on the basis of the presence of the three risk factors from our formula, against the family's wishes, represents an overvaluation of the certitude provided by the formula.
Table 1 of our article contained some errors. We have provided a corrected version, and we apologize for any confusion that may have resulted from the errors.
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Colleen M. Ryan, M.D.
David A. Schoenfeld, Ph.D.
Edwin H. Cassem, M.D.
Ronald G. Tompkins, M.D.
Harvard Medical School
Boston, MA 02114
References
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