Is the influence of social desirability on patients' self-reported adherence overrated?

To the Editor: Adherence is critical to the success of HIV antiretroviral therapy. Accordingly, clinicians need to be able to assess a patient’s adherence accurately so as to inform optimal treatment decision making. Because physicians are poor predictors of a patient’s adherence, accurate and reliable measures of adherence are needed to help clinicians identify patients who need assistance with their pilltaking behavior and to interpret the role of adherence in evaluating clinical outcomes. Electronic monitoring is considered by many to be the current state-ofthe art method of evaluating adherence; yet, this technology is limited by its high cost and the restrictions it places on common adherence strategies (eg, pill boxes, pocketed doses). In contrast, self-report measures are much more practical because of their relatively low cost and ease of administration; however, self-reported rates of antiretroviral adherence average 10% to 20% greater than rates derived from electronic monitoring, and their ability to explain virologic outcomes is inferior to electronic monitoring, resulting in the consensus that self-reports overestimate adherence. The reasons why patients often overestimate their adherence are poorly understood, and there are scarce data on the factors associated with self-report accuracy. We have previously found that patients who take all their doses are nearly always accurate in their selfreport (using electronic monitoring as the validity criterion), whereas only a small proportion (approximately 20%) of patients who miss doses are accurate in their self-report. Self-reports of missed doses are reliable in terms of the patient having actually missed a dose, but the number of doses missed is often inaccurate and underestimated. The aforementioned investigation was not powered to identify patient characteristics associated with self-report accuracy, but there was a trend toward those with lower cognitive functioning (eg, memory problems) being more likely to report adherence inaccurately. Clinicians and researchers often assume that inaccurate self-reports of adherence are a result, at least in part if not mostly, of patients’ social desirability (ie, patients desire to be seen as a “good patient”) and discomfort in disclosing nonadherent behavior. To our knowledge, there has been only 1 investigation that explored the relationship between the accuracy of self-reported adherence and treatment and social desirability, in which no association was detected, although this study investigated adherence to nonmedication treatments. We are not aware of any studies that have examined the relationship between social desirability and medication adherence. Assuming that social desirability influences self-reports, we hypothesized that minimizing social desirability would enhance patients’ accuracy of selfreported adherence. To test this hypothesis, we conducted a pilot study involving a 2-week observation of adherence among persons on HIV antiretroviral therapy. Participants were randomly assigned (using a 2:1 ratio) to either the experimental or control group. Participants in the experimental group were administered a standard 3-day recall self-report adherence measure (similar to that used in ACTG trials) at study end point (week 2), preceded by a discussion of the challenges and difficulties that are commonly associated with adherence to antiretrovirals (enhanced survey). In this brief discussion (approximately 5–10 minutes), the interviewer acknowledges the challenges of treatment and adherence, normalizes lapses in adherence, and encourages the respondent to discuss difficulties with adherence. It was hypothesized that this discussion would reduce discomfort or anxiety that the respondent may have regarding disclosure of nonadherence and therefore result in more accurate reporting of adherence. Participants in the control group did not receive this discussion prior to being administered the adherence measure (standard survey). Electronic monitoring caps (eDEM caps; AARDEX, Zurich, Switzerland) were used to monitor adherence to the antiretroviral with the most complex regimen (defined as the most frequently dosed medication), and these data served as the criterion for evaluating the accuracy of the self-report. Thirty-four participants on HIV antiretroviral therapy enrolled in the study; mean age was 41 years, 82% were male, and 74% were nonwhite. At baseline, mean self-reported CD4 count was 398 (18% <200) and 48% reported having an undetectable viral load. Average length of time on the current antiretroviral regimen was 12 months, and all were on twice-daily dosing regimens. Four participants did not complete the study (1 died of heart failure, 3 were lost to follow-up). Of the 30 study completers, 21 were randomized to receive the enhanced survey (experimental group), whereas the other 9 were administered the standard survey (control group). The sample’s mean electronically monitored adherence rate was 66% (SD = 33) over the entire 2-week observation period and 65% over the past 3 days; mean selfreported adherence (past 3 days) was 83% (SD = 26), which was highly correlated with electronic monitoring (past 2 weeks: R = 0.66, P < 0.001; past 3 days: R = 0.69, P < 0.001). Twelve (40%) participants took all doses (100% adherence) in the past 3 days according to electronic monitoring. Twelve (57%) of the 21 participants in the experimental group accurately reported their adherence compared with 3 (33%) of 9 in the control group (P = 0.21). Among the participants who had missed doses in the last 3 days of the study period (12 in the experimental group, 6 in the control group) as measured by electronic monitoring, however,