This sub-study of the CHECkUP is the first to show that adding the triggerlist as selection criterion in a cohort of older patients (≥ 60 years) with polypharmacy, improves the identification of a population at high risk of MRA, as 48% of the admissions were classified as possibly medication-related by using the AT-HARM10.
The triggerlist was first introduced in the Dutch multidisciplinary guideline for polypharmacy in older patients and was proposed as a list to establish whether a hospital admission is medication-related. Although the triggerlist has high face validity (i.e. the individual components (adverse clinical events) in itself are indeed associated with MRPs and based on data from the HARM-, IPCI- and QUADRAT studies [1, 2, 9, 12, 13]), when it was introduced its use had not been investigated yet. To date, only one study has used the triggerlist and in this study it was used to investigate whether emergency department (ED) visits of patients that were not hospitalized, were medication-related [14]. This retrospective cohort study showed that, based on the triggerlist, half of the ED visits were possibly related to a MRP. Ultimately, medication was deemed as a potential cause in 23% of the respective ED visits and 15.5% was potentially preventable. As such, it was shown that the triggerlist was a good selection criterion for patients in the ED, although consequently a high percentage of false positives was found.
While due to different definitions and the lack of a gold standard the incidence of MRAs varies considerably, it is important to adequately identify the population of interest, i.e. those at high risk of MRA. This is especially important in intervention studies like CHECkUP and other studies that aim to optimize medication in (frail) older patients [10, 15] and although by including older patients with polypharmacy the a-priori risk of a hospitalization being medication-related is already high, we hypothesized that by additionally using the triggerlist as selection criterion, the posteriori probability will increase even further. Although we were, by design, unable to directly test this hypothesis, the current literature supports our assumption and the additional application of the triggerlist as selection criterion as we found 48% of the hospitalizations being medication-related. The incidence of MRAs varies between 5.6% and 30% in adult patients without any risk factors [2, 4, 5, 6, 12] and specifically focusing on older patients, a recent meta-analysis found an incidence of MRAs of 10% [6, 12]. Other studies that select patients with a higher risk for MRAs are the studies of Lea et al. [16] and Zerah et al. [17]. Both studies included older patients (mean age 79 years in both studies) with multimorbidity, defined as ≥ 4 medications of at least 2 ATC groups [16] or ≥ 3 chronic medical conditions and polypharmacy [17]. As such, these studies found a prevalence of hospitalizations being medication-related of 38% and 42%, respectively.
We did not find any significant differences with regard to age, sex, CCI, number of medicines or triggerlist diagnoses/medications when comparing possibly and unlikely MRAs. This is not surprising as in this study, by including only older patients (≥ 60 years) with polypharmacy and two trigger diagnoses, the number of patients using < 5 medicines is minimal and not sufficient to demonstrate a significant association, which is in agreement with Lea et al. [16].
This study is not without limitations. First, the study is limited by its retrospective design. All hospital admissions were evaluated based on the data in the hospital electronic information systems, which were registered by other physicians. We also had no information about compliance or over-the-counter drugs. Second, patients were recruited from a single centre limiting the generalizability of our results. Third, our sample size was relatively small. Although the sample size was deliberately limited to 100 patients (as it was a sub-study of CHECkUP), the point estimate of MRAs has a somewhat greater uncertainty. Finally, when assessing whether a hospital admission was medication-related, the two independent reviewers reached agreement in 64% of the admissions by using AT-HARM10. We believe this might be due to the difference in clinical experience between both reviewers (a pharmacy student and a general pharmacist with 40 years of working experience). Nevertheless, since all discrepancies were discussed by a multidisciplinary panel, which is considered the gold standard, we believe our final point estimate of MRAs is realistic. Despite this, the application of AT-HARM10 in another patient population in another country and also its feasibility still contribute to the further validation of this assessment tool to identify MRAs.