HAART dose missed in the last four days∗ Dose delayed by >2 hours in the last four days∗ HAART dose missed the previous weekend∗ Self-report questionnaire (combining the above three items)∗ At least one missed HAART dose 100% adherent Visual analog scale∗ 2 Yes No Yes No Yes No <9 9 10 No Yes Table 1: Description of the tools used to assess adherence. Antiretroviral drug concentrations (in ng/mL) <1000 for EFV or <3000 for NVP ≥1000 for EFV or ≥3000 for NVP Macrocytosis (MCV > 100 fL)∗∗ ∗Available for 257 patients, ∗∗Available for 252 patients. methods can be undermined by issues of recall bias and social desirability [24]. Antiretroviral (ARV) drug assay [25– 27] and electronic monitoring [28, 29] are more objective but may be too complex and costly for use in developing countries. Macrocytosis, deﬁned as a mean corpuscular volume (MCV) exceeding 100 fL, is common during treat- ment with AZT- and d4T-containing regimens and has been proposed as an alternative and less expensive way of assessing adherence [30]. We therefore conducted a cross-sectional survey of HIV- infected patients receiving NNRTI-based regimens through the ESTHER program in Phnom Penh (Cambodia) in order to identify simpler tools for the identiﬁcation of nonadherent patients and for the prediction of virological failure. 2. Patients and Methods 2.1. Patients. In February 2003, the Cambodian Ministry of Health and the French ESTHER initiative implemented a free treatment program for patients living with HIV/AIDS at Calmette hospital, Phnom Penh. HAART was prescribed according to WHO recommendations (WHO stages III and IV, irrespective of the CD4 cell count, or asymptomatic patients with CD4 cell counts ≤200/µL) both to ARV-na¨ıve patients and to patients having previously paid for ARV themselves. In keeping with national guidelines, ﬁrst-line N (%) 5 (2) 252 (98) 22 (8.5) 235 (91.5) 17 (6.6) 240 (93.4) 34 (13.2) 223 (86.8) 11 (4.3) 62 (24.1) 184 (71.6) 18 (7) 241 (93) 23 (9.1) 229 (90.9) AIDS Research and Treatment therapy consisted of two nucleoside reverse transcriptase inhibitors (NRTIs) plus one NNRTI. The HAART combi- nation was (AZT or d4T)/3TC/efavirenz (EFV) initially, but was then switched to (AZT or D4T)/3TC/nevirapine (NVP) after July 2004, owing to EFV supply problems. Patients were seen in the hospital every month after enrolment, for a physical examination and to record clinical and therapeutic information. On HAART initiation, the patients also entered a therapeutic education program run by nurses. The patients were seen monthly for three months, or more if the educational objectives were not reached (median duration 4.6 months, IQR: 3–6). The adherence study was restricted to patients who had been on HAART for at least six months, to increase the odds that they had met their educational objectives. 2.2. Adherence Assessment. Adherence was assessed in an outpatient clinic. A self-report questionnaire focusing on recent drug intake was administrated. The questionnaire consisted of the following three items: (i) “did you miss any HAART doses during the last four days?,” (ii) “Were you late for any of your intakes by more than two hours during the last four days?,” and (iii) “did you miss any HAART doses last week-end?.” Because of the low educational level of many patients, one-third of the questionnaires were administered by nurses. A visual analog scale similar to that developed for pain evaluation was also used. The patients were asked to position a cursor between “never” (score 1) and “always” (score 10) in response to the question: “In general, would you say you take your treatment. . .?.” Any answer diﬀerent from 10 was considered to represent nonadherence. EFV and NVP plasma concentrations were measured by using high-performance liquid chromatography (HLPC). Patients were asked to come to the clinic in the morning without having taken their daily dose of NVP, and 12 hours after their last dose of EFV. Patients with EFV and NVP concentrations below 1000 ng/mL and 3000 ng/mL, respectively, were considered nonadherent. As all the patients took AZT or D4T, those with an MCV of ≤100 fL were considered nonadherent. A blood sample was collected to determine the CD4 cell count (CyFlow, Partec, Germany) and HIV RNA viral load (ANRS second-generation (G2) real-time RT-PCR) [31]. 2.3. Statistical Methods. All patients who had at least one adherence assessment were included in the analysis. Among the 341 patients meeting the inclusion criteria (including more than 6 months of HAART), 13 patients (3.8%) had died, 14 (4.1%) had been lost to follow-up, 9 (2.6%) had been directed to others centers, 12 were on an LPV/r- containing regimen, 8 were on a triple NRTI combination, and 25 could not be evaluated. A total of 259 patients were ﬁnally included in the analysis. The association between each measure of adherence and virological failure (deﬁned as >400 HIV RNA copies/mL) was tested for signiﬁcance by using the Chi-square test. A logistic regression model was used to evaluate the contribution of