Validity of Behavioral Measures as Proxies for HIV-Related Outcomes

"... although potentially less subject to reporting bias, biomarkers and biologic outcomes have their own flaws."

This research reviews "the literature on the validity of SRs [self-reports] of outcomes most relevant to HIV behavior change interventions, sexual behavior (ever having had sex and condom use), substance use, and medication adherence. We note the extent to which they may be adequate outcome measures without biologic data, and the conditions under which they may be most likely to be sufficient" in order to support the case that, where possible, both SR and biologic measures should be collected in measuring behaviour change in HIV prevention and treatment. The article is from the JAIDS: Journal of Acquired Immune Deficiency Syndromes supplement addressing clinicians and public health scientists in the field of HIV prevention and treatment who might value information on health communication. (Footnotes removed by the editor.)

Findings include the following:

1. Sexual Behaviour - Because a "gold standard" in biologic testing is unavailable for markers of unprotected sex, researchers examined contradictory reporting in research literature. "Percentages ranged from about 4% (for a 2-week interval between measurements) to about 10%-11% for a 1-year interval for US adolescents and up to 16% for a 4- to 6-month time interval for South African adolescents." Compared with other kinds of discrepancies in SR on less sensitive topics, "reports of ever having had sex are only somewhat more discrepant than reports for these much less sensitive variables." For condom use, biomarkers for unprotected sex are limited to markers of semen exposure in women, of which two types of tests are commonly used, and are, as stated here, relatively costly and intrusive.

The use of audio computer-assisted self-interview (ACASI), in which the respondent is alone at the time of answering questions, "has been found to yield prevalences of the most sensitive behaviors that can be as high as 3 times those of prevalences reported using self-administered surveys. Furthermore, the method yields prevalences for a wide variety of behaviors that are 25%-50% higher than those found using other data collection methods."

Two other methodological choices include the appropriate choice of reporting intervals for SRs of behaviour (i.e., condom use over the last week, month, or year) and the use of daily diaries. "In general, 'moderate' reporting periods (3-6 months for condom use, for example, for college students) seem to yield the best data ...", and daily diaries "yield greater frequency of a variety of sensitive behaviors, and thus probably produce more valid results."

Comparison of biologic results for condom use and SRs shows "38% of respondents overreport consistent condom use (i.e., report consistent condom use, although the biomarker suggests at least some intercourse experience(s) during which a condom was not used...", while results of SR compared with sexually transmitted infection (STI) test results show about 80%-90% consistency.

2. Substance Use - Both hair and urine tests exist for tobacco and drug use; and, in testing using biologic markers compared with SR, discrepancies were between 1.5% and 8.8%. Researchers found that biologic tests yielded discrepancies that were "difficult to explain...", while "[s]tatistical models found SRs of perceived privacy and truthfulness of survey responses, as well as religiosity, to be positively associated with validity...." Also, it was shown that asking questions on drug use twice in varying formats and explaining to individuals the necessity for accurate information about their drug use might increase accuracy of SR.

3. Medication Adherence - SR of medication adherence depends upon accurate recall and is limited by patients wanting to please those who treat them, so counting pills in a patient's container at follow-up is another measure. In a comparison experiment of two ACASI questions: (1) self-reported recall of missed doses (SR-recall) and (2) a single-item visual analogue rating scale (VAS), patients were also called, unannounced, to ask for a pill count. The ACASI testing results were consistent with the responses from calls and showed underreporting in SR recall. Prescription checking for refill numbers is another marker, and a fourth method is a Medication Event Monitoring System (MEMS) computer chip cap on a bottle that counts when it is opened. A test of elderly people measured use of multi-compartment compliance aids, for example, refrigerator magnets, stickers on mirrors, pill container for weekly/monthly use, and electronic reminder devices (ERDs - timed alarms, watches, smart phones, and medication containers with computer chips) against health improvements using biologic markers. The intervention group showed improvements over the control group. (As stated here, HIV adherence mirrors general adherence.)

Reminder messages are increasing in use, particularly electronic reminders. "Examples include reminder messages automatically sent to a patient's mobile phone by a short message service (SMS), an ERD that provides patients with an audio and/or visual reminder at predetermined times, and text messages sent to patients' pagers to alert them of their medication....Reminders are especially useful for patients who are unintentionally nonadherent, that is, patients who are willing to take their medication but forget it or are inaccurate in their timing." HIV studies show a significant preference for SMS rather than a beeper (type of ERD), though both seemed effective. 

The research concludes that both SR and biologic measures should be used for all three types of behaviours. "Measurement of key outcomes for HIV behavior change interventions should use methods likely to yield the highest levels of validity of SRs for all 3 types of behaviors. These include using a reporting period that is moderate in length for sexual behavior and substance use, using the best reporting methods available (ie, ACASI for all 3 behaviors and daily diaries under certain circumstances), and using continuing technological improvements such as video or phone-based evidence of medication taking or electronic pill caps to assess medication adherence."