Delirium Identification Algorithms Comparison

We evaluated four different algorithms to identify delirium: 1) ICD diagnosis codes alone, 2) antipsychotics use alone, 3) either ICD diagnosis codes OR antipsychotics use, and 4) both ICD diagnosis codes AND antipsychotics use. For algorithms based on ICD diagnosis codes, delirium was considered present if any of the following 32 explicit (i.e., including the term “delirium”) or implicit ICD-9 diagnosis codes (e.g., “encephalopathy”) was used among the in-hospital discharge codes (see Supplementary Table S1).¹⁴ In claims data from October 1, 2015, the corresponding 52 ICD-10 diagnosis codes were used.¹⁴ For algorithms based on antipsychotics use, delirium was considered present if any antipsychotic drugs were used; in our study, we found that only haloperidol, olanzapine, and quetiapine had been prescribed. We did not examine other drugs that could influence the risk of delirium (e.g., benzodiazepine or dexmedetomidine).