Results

Patient characteristics

Data for 387 patients with 5191 prescriptions at the time of the CMR, with a median of 13 prescriptions per patient (IQR 9 – 17, range 1 – 35), were analysed. The median age of all included patients was 70 years (IQR 58 – 79; range 19 – 102): patients on the Upper GI ward were the youngest, median 68 years (IQR 57 - 75; range 19 – 89] compared with 75 years (IQR 60-84; range 19-102)) for patients on the Internal Medicine ward, and 72 years (IQR 65-80; range 43-88)) for patients on the Otolaryngology and Oncology ward. In total, 172 patients (44.4%) were female: 83 (45.4%) on the Upper GI ward, 78 (48.4%) on the Internal Medicine ward, and 11 (25.6%) on the Otolaryngology and Oncology ward (table 1).
Patients on the Otolaryngology and Oncology ward had the most prescriptions at the time of the CMR (median of 17 (IQR 12 – 19; range 1-32) compared with median 13 (IQR 9-17; range 1-35) on the Upper GI ward, and median on the Internal Medicine ward 9 (IQR 6-13; range 1-31) (table 1).
Patients on the three wards differed (p<0.001) in age; the number of prescriptions at time of the CMR; the number of patients with impaired renal function (eGFR< 50 mL/min according to the CKD-EPI formula); the number of patients with at least one PE; and the incidence of PEs per prescription. There was a non-significant difference in sex (p=0.064) and the number of patients with a documented allergy or intolerance (p=0.68) (table 1).

Prevalence, types and moment of introduction of prescribing errors

Overall, 799 PEs were detected affecting 279 patients (72.1%). The overall incidence of PEs per prescription was 0.15, meaning that in every ten prescriptions, 1.5 PE were detected. In total, 219 PEs were detected that affected 114 patients (62.3%) on the Upper GI ward, 362 PEs were detected that affected 123 patients (76.4%) on the Internal Medicine ward, and 218 PEs that affected 42 patients were detected on the Otolaryngology and Oncology ward. The lowest incidence of PEs per prescription was seen on the Upper GI ward (0.075), and the highest on the Otolaryngology and Oncology ward (0.32) (table 1).
At a patient level, 97.7% of all patients admitted to the Otolaryngology and Oncology ward and selected for a CMR had at least one clinically relevant PE compared with 62.3% (OR 0.039, 95% CI 0.0053–0.29) of patients on the Upper GI ward and 76.4% (OR 0.077, 95% CI 0.010–0.58) of patients on the Internal Medicine ward and (table 1).
Overall, 58.8% of the identified PEs were introduced during hospitalization and 41.7% of these PEs could be defined as ‘overuse’ (table 2) (22). Most (38.1%) PEs involved drugs that were used without an evidence-based clinical indication. The IPS team advised that these drugs should be deprescribed and drew up a plan for this in consensus with ward doctors (table 2). The drug category associated with the most PEs ‘drugs for acid-related disorders’ (ATC code A02), accounting for 13.6% of all identified PEs (supplementary table 2).
While performing CMRs, the IPS team identified a further 49 potential ADEs and these were reported to the Junior Adverse Drug Event Manager team. This resulted in 43 suspected ADRs that were reported to the Netherlands Pharmacovigilance Centre Lareb. The feedback received from the Netherlands Pharmacovigilance Centre Lareb was uploaded into the electronic patient record to enable a patient-specific ADR treatment plan.

Are doctors able to detect patients at risk of PEs?

Forty of the 43 patients (93.0%) on the Otolaryngology and Oncology ward (cases) who were selected for a CMR by the ward doctor were matched to 40 patients admitted to either the Internal Medicine and Upper GI wards and were not selected by the ward doctor(controls). There was no significant difference in age, number of prescriptions, sex, renal function, or allergy or intolerance between the matched cases and the controls (table 3).
The number of patients with at least one PE was significantly higher in the ward physician-selected patients (97.5%) than in the non-selected control patients (72.5%; OR=14.8, 95% CI [1.8 - 121.1], p=0.002). The incidence of PEs per prescription was significantly higher in patients selected by ward doctors than in non-selected control patients (0.33 versus 0.11), which means that the PE rate in patients selected by ward doctors is three times higher than the rate in non-selected control patients (IRR=3.0, 95% [2.3 - 4.0], p<0.001) (table 3).
Comparison of the 304 unmatched patients of the Upper GI- and Internal Medicine wards with the 40 matched controls of these wards revealed a significant difference in the number of prescriptions: 13 prescriptions (IQR 8 – 16, range 1 – 35) versus 16 prescriptions (IQR 11.3 – 19, range 2 – 33) (p=0.005). However, further analysis showed that the matched controls from the Upper GI (N=31) ward did not differ significantly from the unmatched controls from the same ward (N = 152), and the same was true for the matched (n = 9) and unmatched controls (n = 152) from the Internal Medicine ward (supplementary table 1). Thus the 40 controls seem to be representative of the total sample of controls.