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Academia and the Profession |

A Comparison Study of Multiple Measures of Adherence to HIV Protease Inhibitors

Honghu Liu, PhD; Carol E. Golin, MD; Loren G. Miller, MD, MPH; Ron D. Hays, PhD; C. Keith Beck, MD; Sam Sanandaji, BS; Judith Christian, RN; Tomasa Maldonado, RN; Dena Duran, LVN; Andrew H. Kaplan, MD; and Neil S. Wenger, MD, MPH
[+] Article and Author Information

From the University of California, Los Angeles, Los Angeles, and Sheps Center for Health Services Research, Harbor–University of California, Los Angeles, Medical Center, Torrance, California; and University of North Carolina at Chapel Hill and Lineberger Comprehensive Cancer Center, Chapel Hill, North Carolina.


Acknowledgment: The authors acknowledge Victor Gonzalez for technical assistance.

Grant Support: By the National Institute for Allergy and Infectious Diseases (R01 AI 41413).

Requests for Single Reprints: Honghu Liu, PhD, Division of General Internal Medicine and Health Service Research, 911 Broxton Plaza, Room 102, Box 951736, Los Angeles, CA 90095-1736; email, hhliu@ucla.edu.

Current Author Addresses: Dr. Liu: Division of General Internal Medicine and Health Service Research, 911 Broxton Plaza, Room 102, Los Angeles, CA 90095-1736.

Dr. Golin: University of North Carolina Sheps Center for Health Services Research, 725 Airport Road, Suite 208, Campus Box 7590, Chapel Hill, NC 27599-7590.

Dr. Miller: Division of Infectious Diseases, Harbor–University of California, Los Angeles, Medical Center, 1124 West Carson Street, Box 466, Torrance, CA 90509.

Dr. Hays: Division of General Internal Medicine and Health Service Research, 911 Broxton Plaza, Room 110, Los Angeles, CA 90095-1736.

Dr. Beck, Ms. Christian, Ms. Maldonado, and Ms. Duran: Division of Allergy and Clinical Immunology, Harbor–University of California, Los Angeles, Medical Center, 1124 West Carson Street, N-24, Torrance, CA 90502.

Mr. Sanandaji: Division of General Internal Medicine and Health Service Research, 911 Broxton Plaza, Los Angeles, CA 90095-1736.

Dr. Kaplan: 547 Burnett Womack, Campus Box 7030, University of North Carolina School of Medicine, Chapel Hill, NC 27599-7030.

Dr. Wenger: Division of General Internal Medicine and Health Service Research, 911 Broxton Plaza, Room 205, Los Angeles, CA 90095-1736.


Ann Intern Med. 2001;134(10):968-977. doi:10.7326/0003-4819-134-10-200105150-00011
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Background: Poor adherence to HIV protease inhibitors may compromise the effectiveness of treatment. Few studies have compared methods for measuring adherence or have related adherence measures to a clinical outcome.

Objective: To examine the relationship among a composite score of adherence, the three primary measures of adherence, and HIV virologic response.

Design: Longitudinal cohort study.

Setting: Public HIV clinic.

Patients: 108 HIV-infected adults receiving protease inhibitors or non-nucleoside reverse transcriptase inhibitors who were monitored for 666 monthly intervals.

Measurements: Medication Event Monitoring System (MEMS), pill count, and interview combined into a composite adherence score (CAS), and HIV viral load.

Results: Mean antiretroviral adherence differed by adherence measure (MEMS, 0.63; pill count, 0.83; interview, 0.93; and CAS, 0.76). Composite adherence score decreased significantly over time. Composite adherence score, MEMS values, pill values, and interview values were statistically significantly associated with achievement of an undetectable viral load within 6 months of initiating therapy. Composite adherence score showed the strongest predictive relationship (odds ratios for a 10% increase in adherence for CAS, MEMS, pill count, and interview, respectively, were 1.26 [95% CI, 1.16 to 1.37], 1.13 [CI, 1.06 to 1.21], 1.10 [CI, 1.02 to 1.19], and 1.35 [CI, 0.94 to 1.94]).

Conclusions: Different measures applied to the same patient suggest different levels of adherence. Adherence may be underestimated by MEMS and overestimated by pill count and interview. A summary measure combining several measures is more strongly related to a clinical response, but more practical measurement methods are needed for clinical use.

Figures

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Figure 1.
Medication adherence over time by four different measures.MEMSP

Both composite adherence score and Medication Event Monitoring System ( ) have a significant downward change over time (  < 0.05).

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Figure 2.
Receiver-operating characteristic curves for detecting virologic response at week 8.

The lower left corner is the region of the greatest specificity, and the upper right corner corresponds to the highest sensitivity. MEMS = Medication Event Monitoring System.

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Appendix Figure. MEMS = Medication Event Monitoring System.
Algorithm for calculating composite adherence score (CAS).
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