© 2007 American Thoracic Society
From the Authors:Studies focused on the evaluation of patients admitted to the ICU (1) sometimes mix variables evident at the time of admission with other potentially evolutionary criteria that are not applicable to early hospital admission. We have several responses to Dr. Ewig's letter about our recent article (2). The two major criteria of the modified American Thoracic Society (m-ATS) rule, septic shock and mechanical ventilation, are defined in our rule as endpoints since they are potentially evolutionary criteria. Dr. Ewig's characterization that this represents circular logic is incorrect. The inclusion of these criteria focuses squarely on early detection for the following reasons: in our prospective cohort of 1,776 patients, 8 of the 22 patients who presented with shock (36.4%) presented in the emergency department (ED) with a systolic pressure < 90. These eight patients represent 14% of all patients who showed hypotension in the ED. Of the 539 patients who presented with respiratory insufficiency (PO2 < 60), only 2.6% needed mechanical ventilation. There was an important delay between the admission decision in the ED and the appearance of septic shock (8 h on average) or initiation of mechanical ventilation (29 h).
We agree with the suggestion that predictive rules must have high sensitivity. The application of the m-ATS rule in our cohort results in a better positive predictive value than our rule (49.4 vs. 21.4%). However, the sensitivity of the m-ATS rule is much lower than ours (51.3 vs. 92.1%). Our results are in line with previous studies also showing low sensitivity of the m-ATS rule (3–5). Our rule was associated with the development of severe sepsis (p < 0.001), with an acceptable discriminatory rate, and an AUC of 0.87. Severe sepsis could be a reasonable endpoint to add to the definition of severe community-acquired pneumonia, even though we believe that as currently defined severe sepsis lacks the robustness of mechanical ventilation or septic shock. Among the 1,776 patients diagnosed in the ED, 690 presented with severe sepsis. Of these, 6.8% were eventually managed without hospital admission; 36.7% of those admitted to the hospital had a stay of Our rule (2) was not created to evaluate patients who must be admitted to the ICU directly. Instead, it was developed to identify patients who are at risk for an adverse outcome and thus who need additional monitoring and more aggressive treatment after the first evaluation in the ED. What we need to be able to better identify are patients who are at increased risk for an adverse outcome and who thus should be observed at least in an intermediate care unit.
Hospital de Galdakao, Galdakao, Bizkaia, Spain FOOTNOTES Conflict of Interest Statement: None of the authors has a financial relationship with a commercial entity that has an interest in the subject of this manuscript. REFERENCES
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