Health Services Research & Development

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2006 HSR&D National Meeting Abstract


1012 — Incidence and Predictors of All and Preventable Adverse Drug Reactions in Frail Elderly Outpatients

Author List:
Hanlon JT (University of Pittsburgh)
Pieper CF (Duke University)
Schmader KE (Duke University)
Ruby CM (University of Pittsburgh)

Objectives:
The objective was to determine the incidence and predictors of all and preventable ADRs in frail elderly veteran outpatients.

Methods:
The design was a prospective cohort study involving 808 frail elderly who were discharged from 11 Veterans Affairs hospitals to outpatient care. The main outcome measure was number of ADRs per patient as determined by blinded geriatrician and geropharmacist pairs using Naranjo’s ADR algorithm. For all ADRs (possible, probable, or definite), preventability was assessed. Discordances were resolved by consensus conferences.

Results:
Overall, 33% of patients had one or more ADRs for a rate of 1.92 per 1000 person-days of follow-up. The rate for preventable ADRs was 0.71 per 1000 person-days of follow-up. Independent risk factors (p<0.10) for all ADRs were number of medications (Adjusted [Adj.] Hazard Ratio [HR] 1.07, 95% Confidence Interval [CI] 1.05-1.10 per medication), use of benzodiazepines (Adj. HR 1.23, 95% CI 0.95-1.58) and use of warfarin (Adj. HR 1.51, 95% CI 1.22-1.87). Counterintuitively, use of sedative/hypnotics was inversely related to ADR risk (Adj. HR 0.14, 95% CI 0.04-0.57). Similar trends were seen in predictors of preventable ADRs.

Implications:
ADRs are very common in frail elderly outpatients and polypharmacy and warfarin use consistently increase the risk of ADRs.

Impacts:
This is the first study documenting all and preventable ADRs in frail elderly veteran patients recently discharged from hospital and followed as outpatients for up to a one year period. Patient self-report supplemented by chart review appears to be a sensitive method for detecting ADRs in ambulatory care patients. The majority of ADRs occurred in the first few months post discharge and those taking warfarin and multiple drugs are at highest risk.