Screening is the application of a simple test to determine if a patient has a certain condition. For screening to be meaningful in the primary care setting, the particular problem

Must be prevalent within the general population 

Must diminish the duration or the quality of life

Must have an effective treatment available that reduces morbidity and mortality when given during the asymptomatic stage of the disease

Must be detectable via cost-effective screening earlier than without screening and must avoid large numbers of false positives or false negatives

Must be detectable and treatable early enough to halt or delay disease progression and thereby improve outcome

(U.S. Preventive Services Task Force, 1996;National Institute on Alcohol Abuse and Alcoholism, 1993)

Screening for substance abuse, which meets all the conditions above, need not take long and can be conducted effectively in a variety of settings (National Institute on Alcohol Abuse and Alcoholism, 1993).

The Institute of Medicine has recommended that questions about alcohol use be included among routine behavioral and lifestyle questions asked of all persons who seek care in a medical setting (just like questions about diet, exercise, and smoking) (Institute of Medicine, 1990).

The Goal of Substance Abuse Screening

The goal of substance abuse screening is to identify individuals who have or are at risk for developing alcohol- or drug-related problems, and within that group, identify patients who need further assessment to diagnose their substance use disorders and develop plans to treat them (see Chapter 4).

The Consensus Panel that developed this TIP recommends that primary care clinicians periodically and routinely screen all patients for substance use disorders. Deciding to screen some patients and not others opens the door for cultural, racial, gender, and age biases that result in missed opportunities to intervene with or prevent the development of alcohol- or drug-related problems.

Visual examination alone cannot detect intoxication, much less more subtle signs of alcohol- and drug-affected behavior.

A major advantage of conducting substance abuse screening as part of the ongoing process of primary care is that positive screens can be followed up at subsequent visits.

In many practices, clinicians' long-standing relationships with patients give them the opportunity to conduct preliminary assessments also known as brief assessments.

Depending on the clinician's experience and training and the resources available within a community, he may either develop a treatment plan or refer the patient for assessment by a skilled substance abuse specialist.

In larger practices or clinics where provider-patient relationships are not as close, clear documentation of screening results will help ensure appropriate followup.

Negative screens for substance abuse also warrant discussion. They allow clinicians to play a health promotion and prevention role by reinforcing the wisdom of abstinence from illicit drugs and maintenance of safe levels of alcohol use.

If a clinician does not have the time (or the expertise) for a face-to-face discussion of the problem, she can give the patient lists of resources for additional help and a handout or brochure on the effects of alcohol or the other relevant drug. See Appendix D for selected resources.

Factors To Consider in Selecting a Screening Instrument

In the primary care setting, substance abuse screening is done using brief written, oral, or computerized questionnaires, referred to throughout this TIP as screening instruments.

A number of factors must be considered in determining the suitability of a screening instrument for this setting. These include sensitivity and specificity, cost, ease of administration, and patient acceptance.

Sensitivity and Specificity

Sensitivity is a screening instrument's capacity to identify true cases of the target condition in a given population. The closer to 100 percent of those with alcohol and other drug problems that a screen identifies as positive for that condition, the more sensitive the test.

Specificity refers to an instrument's ability to identify people who do not have the disorder. False positives (identifying people who do not have the disorder as having it) tend to increase as sensitivity increases, and false negatives (missed cases) tend to increase as specificity increases.

Because screening instruments are imperfect, balancing sensitivity against specificity is a situation-specific issue. Generally, for screening in primary care, sensitivity should be emphasized over specificity -- that is, it is more important not to miss true cases than it is to assess further some patients who ultimately turn out not to have a substance use disorder.

A positive screen can usually be confirmed or refuted with further history taken on the spot or, if necessary, evaluation by a substance abuse specialist. The screening instruments recommended by the Consensus Panel achieve a reasonable balance between sensitivity and specificity (see Appendix C).

Most screening instruments have been designed for substance abuse treatment populations, not primary care populations.

The four-question CAGE questionnaire (Ewing, 1984) and the Alcohol Use Disorders Identification Test (AUDIT)(Babor et al., 1992), however, have been extensively tested in primary care settings, and a number of other studies of outpatient, substance abuse treatment populations support the practice of applying substance abuse screening instruments to primary care populations (Buchsbaum et al., 1991, 1995;Bohn et al., 1995;Barry and Fleming, 1993;Saunders et al., 1993). The CAGE questionnaire is reproduced below, and the AUDIT appears in Appendix C.

Cost

Costs of administering a screen depend on who does the screening (e.g., physician, nurse, nurse practitioner, or physician assistant), how long it takes, and what special training (if any) is required; whether the instrument can be self-administered by the patient via pencil and paper or computer; and how long it takes to score the instrument.

Ease of Administration

The written questionnaire format is self-explanatory; the interview format consists of a clinician's asking the patient a set of predetermined questions. Computerized versions of validated paper questionnaires such as the CAGE are growing in popularity, and preliminary studies on the effectiveness of this approach are promising (Barry and Fleming, 1990).

A study of adolescents found that when 15-year-olds were asked about past-week alcohol use, 10 percent responded positively to a computerized questionnaire, but only 5 percent to a paper questionnaire (Paperny et al., 1990). Across populations, however, studies have shown that similar results were obtained regardless of the form of the test (National Institute on Alcohol Abuse and Alcoholism, 1993).

Computers also can reduce the time needed for manual scoring and keep track of who has been screened and when. In addition, some computerized screens like the Diagnostic Interview Schedule format (Blouin et al., 1988) will automatically ask selected assessment questions if the score on screening is positive.

Patient Acceptance

Simply raising the subject of substance abuse with patients can be useful. Evidence indicates that asking questions about alcohol or other drugs "primes" patients to disclose information and results in a two- to threefold increase in their stated intention to discuss substance abuse problems with their health care provider in the future (Skinner et al., 1985).

While opinions vary about whether to integrate substance abuse screening into a standard history, asking potentially sensitive questions about substance abuse in the context of other behavioral and lifestyle questions appears to be less threatening to patients. Studies have found that screening for alcohol-related disorders is more acceptable to patients if it is part of a comprehensive health-risk evaluation that covers topics like exercise, diet, weight control, and medication use (Allen et al., 1995).

Placing the questions within the larger context of preventive health care can help both patient and clinician feel more comfortable, reduce any perceived stigma or bias about the questions, and decrease anxiety in the patient.

Members of the Consensus Panel have learned that this finding holds true when screening for use of illicit drugs as well (Fleming and Barry, 1991). Primary care clinicians with experience in substance use screening also report that discussing problematic use can help foster the ongoing relationship between patient and clinician.

Screening Instruments

To expedite screening and increase the likelihood of honest answers, clinicians should ask questions sequentially, beginning with the legal drug alcohol (Institute of Medicine, 1990). Typically people with substance use disorders drink, so asking, "Please tell me about your drinking" serves as an effective filter.

If the patient replies that he does not drink, the clinician should ask, "What made you decide not to drink?" If the answer is that the patient is a life-long abstainer or has been in recovery for 5 years or more, the clinician can conclude the screening process (Steinweg and Worth, 1993).

There are a few exceptions. Even if they don't admit to drinking, adolescents should be asked about drug use, particularly marijuana. Pregnant women and women older than 60, as well as women who have experienced a major life transition (e.g., death of a spouse or retirement), should be queried about their psychoactive prescription drug use and use of over-the-counter sleep aids.

See TIPs 3 (Screening and Assessment of Alcohol- and Other Drug-Abusing Adolescents) and 4 (Guidelines for the Treatment of Alcohol- and Other Drug-Abusing Adolescents) for a full discussion of assessing and treating adolescents (CSAT, 1993b, *1993c) and TIP 2 (Pregnant, Substance-Using Women) for information about that population (CSAT, 1993a).

Substance abuse among people over 60 is covered in a forthcoming TIP, Substance Abuse Among Older Adults (see The National Clearinghouse for Alcohol and Drug Information for TIPs ordering information).

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From SAMHSA/CSAT Treatment Improvement Protocols
TIP 24: A Guide to Substance Abuse Services for Primary Care Clinicians