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Accuracy of Telephone Self-Report of Drug Use in Older People and Agreement with Pharmaceutical Claims Data

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Abstract

Objective

To determine the agreement between two measures of medication use, namely telephone interview self-report and pharmaceutical claims data, in an elderly population.

Methods

An agreement study of 566 community-dwelling, general practice patients aged ≥65 years was conducted to compare self-reported use of medicines with pharmaceutical claims data for different retrieval periods. Classes of drugs commonly used in the elderly were selected for comparison.

Results

1094 people were eligible for the main study. Of these, 697 people completed a follow-up survey and 625 of these patients consented to the release of pharmaceutical claims data. A further 59 participants were excluded from the analysis because they had a home visit instead of a telephone interview. The proportion of observed agreement between the telephone self-report and the various retrieval periods was consistently high. Kappa coefficients showed good to very good agreement (≥0.75) with retrieval periods of 30, 60 and 90 days for benzodiazepines, low-risk NSAIDs, thiazide diuretics and most other drugs. The specificity of self-reported medication use compared with claims data was consistently high across all drug classes, suggesting that people usually did not mention drugs that were not included in the claims data. Sensitivity values varied according to drug class and retrieval period, and were lower for NSAIDs than for benzodiazepines and thiazide diuretics. Decline in sensitivity with increased retrieval periods was most marked for benzodiazepines, NSAIDs and low-risk NSAIDs, which are often used on an as-needed basis. Positive predictive values increased with longer retrieval periods

Conclusion

High agreement and accuracy were demonstrated for self-reported use of medicines when patients were interviewed over the telephone compared with pharmaceutical claims data. The telephone inventory method can be used in future studies for accurately measuring drug use in older people when claims data are not available.

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Acknowledgements

The National and Health Medical Research Council, Australia funded the study but played no role in the formulation of the design, methods, subject recruitment, data collection, analysis or preparation of this paper. SWP received a University of Newcastle Postgraduate Scholarship as a PhD student. The researchers are independent from the funding body. The researchers in the Faculty of Health are members of the Hunter Medical Research Institute.

We thank all the general practitioners (in particular Dr Parker Magin and Dr Peter Hopkins) and their patients for participating in this study; Vibeke Hansen for managing and assisting in data collection; Deborah Bowman for research assistance; Professor Tony Smith, Professor David Henry, Lucy Holt and participating general practitioners for providing extensive advice on development of the content of the medication review checklist; Chris Bonner for advice and providing the Therapeutic Flags manual; Professor Paul Glasziou for developing the grant; the peer reviewers of the thesis for their comments; the Royal Australian College of General Practitioners for approving parts of the research as a clinical audit and as a Continuing Professional Development activity; the National Prescribing Service for approving Practice Incentive Payments; Medicare Australia for providing data; all advisory group members (in particular Judith Mackson [National Prescribing Service] and Professor Kichu Nair) for their advice; all interviewers; and all statisticians involved in this study.

JC (deceased) conceived, designed, analysed and interpreted the results of the study. SWP and JEB designed, analysed and interpreted the results of the study. JC and JB developed the grant. SWP managed and conducted the study and drafted the manuscript. JEB conceived the study, and revised the manuscript. SWP and JEB contributed to the final version. SWP and JEB are guarantors.

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Authors and Affiliations

  1. School of Medicine and Public Health, Faculty of Health, University of Newcastle, Newcastle, New South Wales, Australia

    Sabrina Winona Pit, Julie Ellen Byles & Jill Cockburn

Authors
  1. Sabrina Winona Pit
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  2. Julie Ellen Byles
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  3. Jill Cockburn
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Corresponding author

Correspondence to Sabrina Winona Pit.

Additional information

Professor Jill Cockburn passed away on 13 October 2004. She was an outstanding academic and teacher at the University of Newcastle with a national and international reputation in the field of health behaviour, including healthcare delivery, medical education, teaching interactional skills, quality assurance, quality use of medicines and cancer control.

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Pit, S.W., Byles, J.E. & Cockburn, J. Accuracy of Telephone Self-Report of Drug Use in Older People and Agreement with Pharmaceutical Claims Data. Drugs Aging 25, 71–80 (2008). https://doi.org/10.2165/00002512-200825010-00008

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