• T Kobes, A M Terpstra, IJpmaF F AFFA0000-0002-9420-2732Department of Trauma Surgery, University Medical Center Groningen, Groningen, The Netherlands., LeenenL P HLPH0000-0001-8385-1801Department of Trauma Surgery, University Medical Center Utrecht, PO Box 85500, 3508GA, Utrecht, The Netherlands., R M Houwert, van WessemK J PKJP0000-0002-1166-0990Department of Trauma Surgery, University Medical Center Utrecht, PO Box 85500, 3508GA, Utrecht, The Netherlands., GroenwoldR H HRHH0000-0001-9238-6999Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, The Netherlands.Department of Biomedical Data Sciences, Leiden University Medical Center, Leiden, The Netherlands., and M C P M van Baal.
• Department of Trauma Surgery, University Medical Center Utrecht, PO Box 85500, 3508GA, Utrecht, The Netherlands. t.kobes-2@umcutrecht.nl.
• Arch Orthop Trauma Surg. 2023 Aug 1; 143 (8): 493349414933-4941.

IntroductionNosocomial pneumonia has poor prognosis in hospitalized trauma patients. Croce et al. published a model to predict post-traumatic ventilator-associated pneumonia, which achieved high discrimination and reasonable sensitivity. We aimed to externally validate Croce's model to predict nosocomial pneumonia in patients admitted to a Dutch level-1 trauma center.Materials And MethodsThis retrospective study included all trauma patients (≥ 16y) admitted for > 24 h to our level-1 trauma center in 2017. Exclusion criteria were pneumonia or antibiotic treatment upon hospital admission, treatment elsewhere > 24 h, or death < 48 h. Croce's model used eight clinical variables-on trauma severity and treatment, available in the emergency department-to predict nosocomial pneumonia risk. The model's predictive performance was assessed through discrimination and calibration before and after re-estimating the model's coefficients. In sensitivity analysis, the model was updated using Ridge regression.Results809 Patients were included (median age 51y, 67% male, 97% blunt trauma), of whom 86 (11%) developed nosocomial pneumonia. Pneumonia patients were older, more severely injured, and underwent more emergent interventions. Croce's model showed good discrimination (AUC 0.83, 95% CI 0.79-0.87), yet predicted probabilities were too low (mean predicted risk 6.4%), and calibration was suboptimal (calibration slope 0.63). After full model recalibration, discrimination (AUC 0.84, 95% CI 0.80-0.88) and calibration improved. Adding age to the model increased the AUC to 0.87 (95% CI 0.84-0.91). Prediction parameters were similar after the models were updated using Ridge regression.ConclusionThe externally validated and intercept-recalibrated models show good discrimination and have the potential to predict nosocomial pneumonia. At this time, clinicians could apply these models to identify high-risk patients, increase patient monitoring, and initiate preventative measures. Recalibration of Croce's model improved the predictive performance (discrimination and calibration). The recalibrated model provides a further basis for nosocomial pneumonia prediction in level-1 trauma patients. Several models are accessible via an online tool.Level Of EvidenceLevel III, Prognostic/Epidemiological Study.© 2023. The Author(s).

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