Session Information
Date: Sunday, November 8, 2015
Session Type: ACR Poster Session A
Session Time: 9:00AM-11:00AM
Background/Purpose: Multimorbidity is a major problem in rheumatoid arthritis (RA) but is difficult to measure. Polypharmacy (PP) – co-prescribing an individual multiple medications – is considered a surrogate marker for the burden of multimorbidity. We evaluated the inter-relationships between PP, disease characteristics and acute hospital admissions in a retrospective cohort study of RA patients managed at one large UK specialist centre.
Methods: Routinely captured data were retrospectively analysed. All patients under care at the centre in May 2013 with a diagnosis of RA were included. Information on PP was extracted from the electronic record. Cox proportional hazards were used compare hospitalization risk according to levels of PP over the subsequent 18-months. Follow up was censored at date of first admission or study end, whichever came first. Further analysis explored relationships between DMARD prescribing and hospitalisation risk. All acute admissions were manually reviewed by two independent clinicians and adjudicated to determine whether an adverse drug reaction (ADR) or drug interaction was implicated.
Results: 1,101 RA patients were studied; their baseline features are shown in the table. The mean number of medications was 5, 29% of patients were on 6-9 medications and 11% on ≥10 medications. PP correlated with increasing age, longer disease duration, higher disease activity and disability (Table). In total 173 patients had at least one unplanned admission during follow up (overall incidence 11/100 patient years (95% CI 9 to 13). Patients on ≥10 medications had an age and gender adjusted hazard ratio for hospitalisation of 3.1 (95% CI 2.1 to 4.5) compared to those on <6. Different DMARD prescription strategies were not significantly associated with hospitalisation risk; steroid use associated with a doubling in risk 2.3 (95% CI 1.6 to 3.1). The most common reason for hospitalisation was infection 44/173 (28%), which was not significantly different across PP strata (p= 0.242). In half of all admissions, an ADR was a possible contributing factor. However, only 4 admissions were definitely a direct result of an ADR. Of these, 2 were related to over anticoagulation, 1 in the setting of co-prescription of leflunomide with warfarin.
Conclusion: PP is prevalent in RA patients and correlates to more severe disease as well as a higher rate of hospitalisation. What is unclear is whether or not PP is harmful. Review of the individual hospitalisations revealed very few admissions definitely attributable to an adverse drug reaction. However, there were many possible relationships (e.g. in cases of infection in patients on DMARDs), making a true understanding of the causal relationship between PP and hospitalisation unclear. Irrespective, PP does appear to reflect comorbidity well and represents a useful tool to adjust for confounding in epidemiologic analyses.
Table
|
Baseline characteristic |
|||||
|
All patients |
0-5 medications |
6-9 medications |
≥10 medications |
p value* |
|
|
Number of subjects, n |
1101 |
658 |
320 |
123 |
|
|
Age |
61.34 (16.00) |
57.6 (16.3) |
66.6 (14) |
67.7 (13.3) |
0.0001 |
|
Gender (% female) |
78.8 |
76.8 |
83.1 |
78.1 |
0.07 |
|
DAS28 mean (SD) |
3.65 (1.61) |
3.33 (1.60) |
4.06 (1.56) |
4.24 (1.38) |
0.0001 |
|
HAQ (SD) |
1.35 (0.93) |
1.02 (0.90) |
1.66 (0.81) |
2.04 (0.74) |
0.0001 |
|
Disease duration (SD) |
10.42 (9.93) |
9.15 (8.66) |
11.93 (10.68) |
13.45 (12.92) |
0.0002 |
|
DMARD prescribing strategy (%) |
|||||
|
Mono |
45 |
49 |
42 |
32 |
0.001 |
|
Dual |
26 |
24 |
29 |
27 |
0.19 |
|
Triple |
8 |
7 |
8 |
12 |
0.09 |
|
Biologic |
22 |
17 |
33 |
19 |
<0.000 |
|
Hospitalisation data |
|||||
|
Exposure (person-years) |
1599 |
983 |
469 |
147 |
|
|
Events, n |
173 |
75 |
50 |
48 |
|
|
Incidence /100 years (95% CI) |
7.6 (6.1, 9.6) |
10.7 (8.1, 14.1) |
32.6 (24.6, 43.2) |
||
|
Unadjusted HR (95% CI) |
Ref |
1.4 (1.0, 2.0) |
4.2 (2.9, 6.0) |
||
|
Adjusted HR (95% CI) |
Ref |
1.0 (0.7, 1.5) |
3.1 (2.1, 4.5) |
||
|
Analysis of causal relationship between medication and admission |
|||||
|
Was an ADR responsible for the admission |
Definitely |
Probably |
Possibly |
Unlikely |
|
|
n (%) |
4 (2.3) |
8 (4.6) |
74 (42.8) |
87 (50.3) |
|
|
If and ADR was implicated, was an RA drug involved, n (% of ADRs) |
2 (50) |
4 (50) |
39 (52.7) |
N/A |
|
|
Corticosteroid involved, n |
0 |
0 |
8 |
N/A |
|
|
Any DMARD involved, n |
2 |
3 |
26 |
N/A |
|
|
Biologic involved, n |
0 |
3 |
9 |
N/A |
|
|
Was a major drug-drug interaction present on the admission medication, n |
2 |
3 |
6 |
N/A |
|
|
Were any minor drug-drug interactions present on the admission medication, n |
1 |
5 |
57 |
N/A |
|
|
*p value for significance across medication strata using either Kruskal Wallis or Chi2 (for dichotomous variables) tests |
|||||
To cite this abstract in AMA style:
Filkova M, Carvalho J, Norton S, Scott DL, Mant T, Cope AP, Molokhia M, Galloway J. Polypharmacy Is a Predictor of Hospitalisation in Patients with Rheumatoid Arthritis [abstract]. Arthritis Rheumatol. 2015; 67 (suppl 10). https://acrabstracts.org/abstract/polypharmacy-is-a-predictor-of-hospitalisation-in-patients-with-rheumatoid-arthritis/. Accessed .« Back to 2015 ACR/ARHP Annual Meeting
ACR Meeting Abstracts - https://acrabstracts.org/abstract/polypharmacy-is-a-predictor-of-hospitalisation-in-patients-with-rheumatoid-arthritis/