Outcome of AIDS patients requiring mechanical ventilation predicted by recursive partitioning

Mechanical ventilatory support (VS) is often required for patients with AIDS. Patients, and/or their surrogates often ask the likely outcome of this intervention. To answer this question, we have developed a classification tree using clinical data from 71 patients with AIDS identified from the discharge abstracts of two hospitals between January 1990 and September 1994. These data were obtained at the time of hospital admission prior to any treatment and before VS was initiated. Survival was defined as discharge from the hospital that occurred in 13 of 72 admissions reviewed. A classification tree was developed by binary recursive partitioning. The output of the resulting tree was adjusted to produce a positive predictive value for death of 100% (95% confidence interval [95% CI], 94 to 100%) and a sensitivity and specificity of 98% (95% CI, 91 to 100%) and 100% (95% CI, 74 to 100%), respectively. The negative predictive value was 92% (95% CI, 64 to 100%). The tree predicted that patients with lactate dehydrogenase (LDH) levels less than 1,176 IU/L survived until hospital discharge, unless they had a positive blood culture, active tuberculosis prior to VS, a blood CD4 count less than 12 cells per cubic millimeter, or creatinine and hemoglobin values that were either above 2.4 mg/dL or less than 8.5 mg/dL, respectively. The remainder of the patients with an LDH level above 1,176 IU/L in this study died before hospital discharge. The classification tree requires prospective validation before it can be used as a predictive instrument. Nevertheless, this approach can be used to develop a concise summary of the local outcome experience of this circumstance in a manner that could be conveyed to patients and/or their surrogates.