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Adherence and Viral Load in HIV-Infected Drug Users: Comparison of Self-Report and Medication Event Monitors (MEMS) J. ARNSTEN*1, P. DEMAS1, M. GOUREVITCH1, D. BUONO1, H. FARZADEGAN2, and E. SCHOENBAUM1.
1Montefiore Med. Ctr., Bronx, NY and 2Johns Hopkins Sch. of Hygiene and Publ. Hlth., Baltimore, MD Objective: To describe the relationship between HIV viral load and both self-reported (SR) and MEMS adherence, subjects currently taking combination antiretrovirals were recruited from a longitudinal study of methadone-maintained HIV-infected drug users.
Methods: Over a median study period of 170 days, viral load and adherence with all antiretrovirals (mean=3 drugs per patient) were assessed by SR and MEMS at each of 6 monthly interviews.
Results: 303 SR estimates and 281 MEMS estimates were obtained from 62 patients. To accurately compare SR to MEMS, both measures were calculated separately (%adherence=doses taken/doses prescribed) for 1 week and 1 day prior to each interview. Mean SR adherence for 1 week correlated with mean SR adherence for 1 day (77% v. 79%; r=0.8, p<0.001, range=0-100%), as did mean MEMS adherence for 1 week and 1 day (53% v. 56%; r=0.92, p<0.001, range=0-100%). Though MEMS and SR were correlated (r=0.5, p<0.01), SR adherence was overestimated by a mean of 33% (range=0-93%). Both SR and MEMS were associated with viral load (p<0.001 for 1 week, p<0.01 for 1 day), but viral load was undetectable in 75% of patients with >95% adherence by MEMS, compared to 63% with >95% adherence by SR. Similarly, viral load was undetectable in 60% of patients with 85-95% MEMS adherence, compared to only 44% with 85-95% SR adherence. Active cocaine use was the only factor associated with overestimating SR adherence (mean overestimate of adherence=48% for active users v. 25% for non-users, p=0.01), and was also associated with poor MEMS adherence (35% v. 60%, p=0.01). Other factors associated with poor MEMS adherence included female gender (31% for women v. 61% for men, p=0.02) and not receiving SSI/disability benefits (42% v. 59%, p=0.06).
Conclusions: HIV viral load is more strongly associated with 1 week adherence than 1 day adherence for SR and MEMS, demonstrating the advantage of 1 week estimates. SR overestimates MEMS, and high SR adherence is less predictive of virologic suppression than high MEMS adherence. Treatment of cocaine dependence may increase adherence in HIV-infected drug users.
Key Words: adherence, drug users, MEMS
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