Predicting the risk of documented ventilator-associated pneumonia for benchmarking: Construction and validation of a score*

Objectives:To build and validate a ventilator-associated pneumonia risk score for benchmarking. The rate of ventilator-associated pneumonia varies widely with case-mix, a fact that has limited its use for measuring intensive care unit performance. Methods:We studied 1856 patients in the OUTCOMEREA database treated at intensive care unit admission by endotracheal intubation followed by mechanical ventilation for >48 hrs; they were allocated randomly to a training data set (n = 1233) or a validation data set (n = 623). Multivariate logistic regression was used. Calibration of the final model was assessed in both data sets, using the Hosmer-Lemeshow chi-square test and receiver operating characteristic curves. Measurements and Main Results:Independent risk factors for ventilator-associated pneumonia were male gender (odds ratio = 1.97, 95% confidence interval = 1.32–2.95); SOFA at intensive care unit admission (<3 [reference value], 3–4 [2.57, 1.39–4.77], 5–8 [7.37, 4.24–12.81], >8 [5.81 (3.2–10.52)], no use within 48 hrs after intensive care unit admission of parenteral nutrition (2.29, 1.52–3.45), no broad-spectrum antimicrobials (2.11, 1.46–3.06); and mechanical ventilation duration (<5 days (1); 5–7 days (17.55, 4.01–76.85); 7–15 days (53.01, 12.74–220.56); >15 days (225.6, 54.3–936.7). Tests in the training set showed good calibration and good discrimination (area under the curve-receiver operating characteristic curve = 0.881), and both criteria remained good in the validation set (area under the curve-receiver operating characteristic curve = 0.848) and good calibration (Hosmer-Lemeshow chi-square = 9.98, p = .5). Observed ventilator-associated pneumonia rates varied across intensive care units from 9.7 to 26.1 of 1000 mechanical ventilation days but the ratio of observed over theoretical ventilator-associated pneumonia rates was >1 in only two intensive care units. Conclusions:The ventilator-associated pneumonia rate may be useful for benchmarking provided the ratio of observed over theoretical rates is used. External validation of our prediction score is needed.

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