402 CHAPTER 5 3.1. The risk of a drug-related hospital readmission The primary outcome of the OPERAM trial was a patient’s first hospital readmission that was considered a drug-related admission (DRA), within one year after inclusion. A DRA was defined as a ‘hospitalisation due to an adverse drug event; harm due to an adverse drug reaction or a medication error related to overuse, underuse, or misuse of prescription and non-prescription medications and which is the main reason for or contributes to hospital admission of a patient’ [57]. DRAs were not significantly reduced in the intervention group compared to the control group, and no betweengroup difference was found for any hospital readmissions or potentially preventable DRAs. A first hospital readmission occurred in 46.4% (n = 447/963) of total intervention patients compared to 49.4% (n = 516/1045) of total control patients. In patients who were readmitted, 47.2% (n = 211/447) of intervention patients and 45.3% (n = 234/516) of control patients had a drug-related readmission. The preventability of drug-related readmissions was defined as readmissions related to potential medication errors (i.e. drug overuse, underuse, or misuse). A DRA was considered preventable in 39.8% (84/211) of intervention patients and in 42.7% (n = 100/234) of control patients. A summary of the results of the OPERAM trial (Chapter 3.1) and of the different steps in the medication review process (Chapters 4.1–4.3) appear in Figure 1. The outcome of a DRA requires clinical consideration, including a causality assessment. Thus, a DRA remains a partially subjective outcome as it relies on the quality of documented information available for adjudication. Unsurprisingly, reported incidences of DRAs have varied greatly in the literature due to differences in definitions, study populations and assessment methods [58]. Thus, the intervention and outcome variability further complicates establishing a causal relationship between a medication review and the outcome of a DRA. Therefore, the adjudication process in OPERAM was performed by skilled senior clinician pairs who were blinded for patient allocation using a standardised adjudication guide to maximise reliability of this outcome [59,60]. Hence, difficulties that may have arisen in the adjudication process were similar for OPERAM intervention and control patients and would not likely have affected the primary outcome. However, a DRA remains a broadly defined outcome measure that can occur in any patient using medication over time. Although observational studies identified certain drugs (or a lack of indicated drugs) posing an increased risk of DRAs in older people, this outcome remains open to multiple interpretations of risk factors associated with each drug therapy related to individual patient characteristics at a certain moment in time. Inappropriate prescribingmay increase the risk of a DRA but does not necessarily result in a DRA. Conversely, interventions to optimise drug therapy may positively affect the risk of drug-related harm, but the risk of a DRA can remain substantial in a patient with polypharmacy andmultimorbidity, as explained by combining Examples 1 and 2 (Box 3).
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