93 5 DELIRIUM | PART THREE Table 1. Predisposing and precipitating factors for delirium (continued) Precipitating factors Group Factor Cut-off Intracranial neoplasm Primary tumor Metastasis Carcinomatous meningitis Organ failure Pulmonary failure O2 sat <88% or PO2 <55 mm Hg Renal insufficiency creatinine >312 mmol/liter (3xULN) or creatinine >3 x baseline Liver failure Bilirubin >60 mmol/liter (3x ULN) and/or ASAT >150 U/liter (5x ULN) and/or ALAT >200 U/liter (5x ULN) Cardiac failure Requiring (prolonged) hospitalization Metabolic disturbance Calcium (corrected for albumin level) <1.75 mmol/liter >3.1 mmol/liter Sodium <130 mmol/liter >155 mmol/liter Potassium <3.0 mmol/liter >6.0 mmol/liter Glucose <2.2 mmol/liter >13.9 mmol/liter Albumin <20 g/liter Development of a delirium prediction algorithm Based on the predisposing factors and the grouped variables for the precipitating factors a prediction algorithm was developed. For the development of this prediction algorithm, the groups were defined irrespective of the prevalence rates of the individual factors to limit the number of factors included (see Table 1). Grouped variables were defined positive if any of the factors in this group was present. Eastern Co-operative Oncology Group (ECOG) performance status (0-2 vs. 3-4), palliative or curative treatment intention, and whether or not an admission was scheduled, were also included in the prediction algorithm. For prediction models, it is recommended that the number of events should ideally be 10-fold higher than the number of variables included in the model [20]. Therefore, we enriched the database with 46 extra delirium cases that were consecutively diagnosed with DOSS screening between July 2012 and September 2013 (Table 2). These baseline characteristics of these cases did not significantly differ from the patients with delirium in the original dataset. The enriched database is suitable for the calculation of odds ratios and the identification of predictors, but not for the calculation of absolute risks [21]. The absolute risks were calculated from the original database.
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