Journal Club Alcohol, Other Drugs, and Health: Current Evidence July–August 2010

Featured Article A Single-Question Screening Test for Drug Use in Primary Care Smith PC, et al. Arch Intern Med. 2010;170(13):1155–1160.

Study Objective To validate a single-question screening test for drug use and drug use disorders a in primary- care setting.

Study Design Adult patients were recruited from a primary-care clinic waiting room in a large US urban medical center. To minimize bias, potential subjects were approached using a predetermined pattern based on waiting-room seating. Exclusion criteria were as follows: –Age <18 years –Very limited English language skills –Cognitive impairment –Acute illness –People accompanying patients but not patients themselves

Study Design (cont’d) Of the 394 eligible patients approached, 286 (73%) completed the screening interview. Participants were asked the following question: “How many times in the past year have you used an illegal drug or used a prescription medication for nonmedical reasons?” –A response of ≥1 time was considered positive for drug use. Participants then completed the 10-item Drug Abuse Screening Test (DAST), the Short Inventory of Problems– Drug Use (SIP-DU), and the Composite International Diagnostic Interview—Substance Abuse Module (CIDI- SAM). Responses were compared with oral fluid testing for illegal drugs.

Assessing Validity of an Article About Diagnostic Tests Are the results valid? What are the results? Will the results help me in caring for my patients?

Are the Results Valid? Was there an independent, blind comparison with a reference standard? Did the patient sample include an appropriate spectrum of patients to whom the diagnostic test will be applied in clinical practice? Did the results of the test being evaluated influence the decision to perform the reference standard? Were the methods for performing the test described in sufficient detail to permit replication?

Was there an independent, blind comparison with a reference standard? The CIDI-SAM was used as the reference standard, as were results of oral fluid testing in the 240 patients (84%) who consented to it. Data were recorded anonymously, unaccompanied by any unique identifiers. It is not clear whether the research staff who conducted the interviews also analyzed the data.

Did the patient sample include an appropriate spectrum of patients to whom the diagnostic test will be applied in clinical practice? Yes. The population included all comers to a primary care clinic and the sample included the spectrum from no drug use through dependence.

Did the results of the test being evaluated influence the decision to perform the reference standard? No. –Both the single-question screen and reference standard (CIDI-SAM) were administered to all subjects. Saliva testing was not related to the results of the screening test, although not all subjects agreed to testing.

Were the methods for performing the test described in sufficient detail to permit replication? Yes. –The verbatim screening question was provided in the article.

What Are the Results? Are the likelihood ratios for the test results presented or data necessary for their calculation included?

Are the likelihood ratios for the test results presented or data necessary for their calculation included? Yes. –The sensitivity, specificity, likelihood ratios, and area under the receiver operating curve (AUC) of the single- question screen were calculated for detection of drug use drug use associated with problems, and presence of a current drug use disorder. –For comparison, the same ratios for detection of the same conditions were calculated for the DAST-10.

Will the Results Help Me in Caring for my Patients? Will the reproducibility of the test result and its interpretation be satisfactory in my setting? Are the results applicable to my patients? Will the results change my management strategy? Will patients be better off as a result of the test?

Will the reproducibility of the test result and its interpretation be satisfactory in my clinical setting? Administration of the test and its results might differ if asked by clinical versus research personnel. Similarly, since responses were recorded anonymously in this study, the same level of validity might not be expected in a clinical setting if recorded in a medical record.

Are the results applicable to the patients in my practice? Results likely apply to, at least, urban primary care settings. A high proportion of the sample had substance use disorders, reflecting the high substance-use prevalence in the studied practice. Non-English speakers were excluded. 54% of participants were women. The majority of patients identified themselves as black (63%), 17% as white, and 16% as Hispanic. Results differed little by sex or race/ ethnicity.

Will the results change my management strategy? In circumstances in which it would be useful to screen for drug use and drug-use disorders, the validity and brevity of the screening question may make screening easier.

Will patients be better off as a result of the test? Identification of drug use by screening might avoid drug interactions and other diagnostic and therapeutic errors, and paves the way for early intervention. Whether patients are in fact better off will depend on follow up of positive screens with skillful assessment, intervention, and/or referral to specialized treatment.

Summary/Clinical Resolution The single screening question accurately identified drug use in this sample, supporting its usefulness in primary-care settings. Although it cannot detect drug-use severity, positive single-question screens can serve as indicators that further assessment is warranted. This study had the following limitations: –The proportion of participants reporting substance use disorders was high, limiting the generalizability of results. –Participants were assured anonymity. This improves the accuracy of the reference standard interview, but may serve to overestimate the accuracy of the screening test itself.