Secondary Logo

Journal Logo

Letter to the Editor

Application of a 3-Item Adherence Metric to Monitor Antiretroviral Medication Adherence in a Resource-Limited Setting

Apisarnthanarak, Anucha MD*; Mundy, Linda M MD, PhD

Author Information
JAIDS Journal of Acquired Immune Deficiency Syndromes: December 1, 2010 - Volume 55 - Issue 4 - p 528
doi: 10.1097/QAI.0b013e3181eec0c4

To the Editors:

Adherence to antiretroviral therapy (ART) is critical for treatment success and has consistently correlated with clinical outcomes in HIV infection.1-3 The 72-hour recall metric (RM) has been regarded as a standardized self-report metric in various Adults AIDS Clinical Trial Group trials.4 Although the 72-hour RM is validated, it unfortunately is lengthy, contains a series of redundant stem questions, and requires adequate resources for administration and scoring. A recent comparison of adherence metrics in a US multicohort analysis suggested that the 3-item Center for Adherence Support Evaluation (CASE) adherence index was easy to use and correlated well with the 72-hour RM among persons on ART for HIV infection.5 Use of this metric has not been reported in non-US settings. We conducted a prospective study to evaluate the use of the 3-item CASE metric in Thai patients on ART for HIV infection.

From July 31, 2007, to June 31, 2008, all HIV-infected ART-naive patients who were starting on GPO-VIR (stavudine, lamivudine, and niverapine) in the HIV clinic at Thammassat University Hospital were eligible. Patients who consented were enrolled in an 18-month assessment of ART medication adherence evaluated by self-report using the 3-item CASE metric (see Appendix, Supplemental Digital Content, and pill counts at both scheduled visits and unannounced home visits. At each routine medical encounter, the patient met face-to-face with a pharmacist who verbally administered the 3-item CASE metric and calculated the ratio of pills taken divided by the total number of pills prescribed for the interval period. Random, unannounced home visits were conducted by trained adherence counseling educators twice monthly and included pill counts. Mean medical visit compliance and pill counts (scheduled and unannounced) were calculated for each 6-month period of observation, and patients were tested for HIV viral load every 6 months. Treatment success was defined as viral load ≤400 copies per milliliter at month 6 and viral load ≤50 copies per milliliter at months 12 and 18.

There were 204 patients who consented to study participation; 106 (52%) were men, the median age was 32 years (range 14-65 years), 163 (80%) had prior opportunistic infections, and the baseline median CD4 count was 74 cells per milliliter (range 5-240 cells/mL). At 6, 12, and 18 months, HIV suppression <50 copies per milliliter was achieved by 199 (98%), 198 (97%), and 196 (96%) participants, respectively. At 6-month follow-up, all 199 participants with treatment success had CASE metric scores >12 and ≥75% visit compliance; 192 (96%) had ≥75% adherence measured by scheduled and unannounced pill counts. At 12-month follow-up, all 198 participants with treatment success had CASE metric scores >12, 196 (99%) had ≥75% visit compliance, and 191 (97%) had ≥75% adherence measured by scheduled and unannounced pill counts. At 18-month follow-up, all 196 patients with treatment success had CASE metric scores >12, 195 (99%) had ≥75% visit compliance, and 190 (97%) had ≥75% adherence measured by scheduled and unannounced pill counts. Overall, during the 18-month study period, there was high correlation between a 3-item CASE metric score >12 and visit compliance >75% (r = 0.83) and combined scheduled and unannounced pill counts (r = 0.79). The sensitivity of a composite score >12 was higher than a >10 cut-off score for adherence (100% vs. 94%, respectively) with the 3-item CASE metric.

Our study findings suggest that the 3-item CASE metric correlated well with subjective ART medication measures such as visit compliance ≥75% and scheduled and unannounced pill counts ≥75%. In this Thai population studied in 2007-2008, a CASE metric score >12 was associated with higher sensitivity than the score >10 that was identified in the original cross-site evaluation of 11 US study sites from 1999 to 2002.5 Two plausible distinctions for the differential cut-offs for this metric may be the secular trends in HIV care over time and the simplified GPO-VIR regimen in the Thai population, and that at the original CASE metric was part of an exploratory analysis in marginalized populations whereby most participants were treatment experienced and had ongoing problems with drug use, homelessness, and drug-resistant HIV infection.5 Independent of these differences, the ease in administration and scoring of the 3-item CASE metric contributes to the promotion of its use as an ART adherence tool in routine HIV care in this middle-income country.

Anucha Apisarnthanarak, MD*

Linda M. Mundy, MD, PhD†

*Division of Infectious Diseases, Thammasat University Hospital, Pratumthani, Thailand

†LLC, Bryn Mawr, PA


1. Bangsberg DR, Hecht FM, Charlebois ED, et al. Adherence to protease inhibitors, HIV-1 viral load, and development of drug resistance in an indigent population. AIDS. 2000;14:357-366.
2. Garcia de Olalla P, Knobel H, Carmona A, et al. Impact of adherence and highly active antiretroviral therapy on survival in HIV-infected patients. J Acquir Immune Defic Syndr. 2002;10:105-110.
3. Hogg RS, Heath K, Bangsberg D, et al. Intermittent use of triple-combination therapy is predictive of mortality at baseline and after one year of follow-up. AIDS. 2002;16:1050-1058.
4. Paterson, DL, Swindells S, Mohr J, et al. Adherence to protease inhibitor therapy and outcomes in patients with HIV infection. Ann Intern Med. 2000;133:21-30.
5. Mannheimer SB, Mukherjee R, Hirschhorn LR, et al. The CASE adherence index: A novel method for measuring adherence to antiretroviral therapy. AIDS Care. 2006;18:853-861.

Supplemental Digital Content

© 2010 Lippincott Williams & Wilkins, Inc.