A single-question screen was sensitive and specific for the detection of drug use and drug use disorders in a sample of primary care patients. Its test characteristics were similar to those of a longer screening tool in this sample, as well as in other studies reported in the literature4
Drug use is prevalent in primary care1
. While national guidelines do not currently recommend universal screening for drug use in primary care, recent evidence supports the effectiveness of brief intervention in this setting and screening, brief intervention and referral to treatment (SBIRT) initiatives are widespread3, 17
. In addition to identifying patients who might benefit from brief physician counseling, drug use screening is likely worthwhile in many clinical circumstances, such as identifying potential medication interactions and prescribing risks (as when clinicians ask patients to report prescription and over-the-counter medication use and alternative medicines as part of routine care).
Time constraints in the primary care setting have been cited as a reason for failure to provide screening and prevention in general (according to one estimate, providing all recommended preventive services to an average primary care panel would require 7.4 hours out of each work day)18
. Successful screening and brief intervention programs therefore require a means of quickly selecting, from among all primary care patients, those most likely to benefit from further assessment and intervention. Single-question screening tests for unhealthy alcohol use have been validated and one such test is currently recommended by the National Institute on Alcohol Abuse and Alcoholism (NIAAA) in its most recent clinician’s guide6
. To our knowledge, no other single-question screening test for drug use has been validated in any setting. Such a screening test could facilitate the early identification and brief intervention, as well as the avoidance of prescription errors and associated risks.
A number of drug use screening instruments have been proposed for use in general medical settings, ranging from two questions to over 705, 19
. Some of these are modified versions of alcohol screening tests and some ask simultaneously about both alcohol and drugs (so-called conjoint screens). Conjoint screens may be more acceptable to some patients than direct questioning about drug use, but also require more clarification of a positive screen, and some of the questions, adapted from alcohol screening tests, may be less applicable to drug use (e.g. the “eye-opener” question from the CAGE-AID)20
. A brief, two- item conjoint screen (TICS) has been validated, representing a screening strategy of equivalent brevity to asking a single question about drug use and a single question about alcohol. The TICS was 79% sensitive and 78% specific for either an alcohol or drug use disorder. The sensitivity for a drug use disorder was similar, but specificity was not reported19
. Two longer, but still brief, conjoint screens, the CAGE-AID and RAFFT have been tested in adults, with similar test characteristics20, 21
. These conjoint tests target drug disorders but do not specifically identify drug use.
The DAST (not validated in a primary care sample until this present paper), DUDIT (only validated in criminal justice and detoxification settings) and ASSIST, three screening questionnaires that ask about drug use specifically, have better test characteristics than the shorter conjoint screening tests and address part of the spectrum of clinical interest beyond drug diagnoses to include use and problems, but their length (between 10 and 28 questions for the DAST and over 70 questions for the ASSIST) and the need for scoring represent significant barriers to their use as screens in the primary care setting4, 5, 22
. As a screening test (as opposed to an assessment of severity or a diagnostic tool) the single-question screen performed almost as well as the longer DAST-10 in the sample that we studied. Longer screening tools may however have promise as electronic record systems with decision support become more widespread (and as evidence for the validity of the ASSIST accumulates), potentially as a follow up assessment after a positive single-question screen, or even as a written pre-visit questionnaire. In summary, in terms of brevity, ease of scoring, and validity for detecting the spectrum of drug-use conditions of interest in primary care, and therefore, likely greater widespread implementation, the single-question screen appears to have favorable characteristics.
In order for a screening test for drug use to be useful it must be applicable to the broad range of people seen in primary care. The diversity of our subject sample allowed us to examine the effect of gender, ethnicity, primary language and education on the accuracy of the single-question screen. While variations were seen in the sensitivity and specificity of the test across these groups, the differences were small.
Our study has several limitations. A higher than expected proportion of subjects reported substance use disorders, likely reflecting the fact that they were recruited from an urban safety-net hospital located in a community where the prevalence of such problems is high. While this potentially limits the generalizability of our results, it is this type of high risk population that is typically targeted for screening and brief intervention (as previously mentioned, universal screening of all adults is not currently recommended whereas targeted screening is recommended)23
. Nevertheless, further study of the screening question in other settings (as well as in other language and in written and computer based versions) is warranted. Subjects were also assured anonymity, a condition which improves the accuracy of the reference standard interview but which may also serve to over-estimate the accuracy of the screening test itself. This is consistent, however, with the methodology of most other studies of screening tests for substance use disorders, thus allowing comparability of our findings with those of other studies.
The single-question screen accurately identified primary care patients who use drugs. Some patients who screen positive will have severe drug use disorders requiring referral to substance abuse treatment, while those who use drugs but have not experienced severe health or interpersonal problems might benefit from brief intervention by the primary care provider. The lack of an efficient way to distinguish these two groups is a challenge that must be addressed when implementing screening for drug use. The DAST and the ASSIST, in providing scores, provide a measure of severity. Even though they may be too long for universal screening in many settings, they might be done as assessments after a single-item screening question is answered in the affirmative. But this approach has not been tested or validated.
The single-question screen accurately identified a broad spectrum of drug use in this sample of primary care patients. The sensitivity and specificity of this single question was comparable to that reported for longer instruments in other studies. These findings support the use of this brief screen when identification of drug use is desired in primary care settings, which should, in turn, facilitate the implementation of screening and brief intervention programs in this setting.