Bio-Rad Laboratories (www.bio-rad.com) offers a reagent kit (%CDT Turbidimetric Immunoassay). It quantifies CDT as a percent of total serum transferrin, rather than total CDT, thus correcting for individual variations in transferrin levels. CDT values are obtained from a 100-microliter serum sample. The blood is clotted and the serum separated. The sample may be stored at 2 to 8 °C if the test is to be run within 1 week. Samples must be tested at a reference lab (Bio-Rad offers a list of labs). Results are available in a few days.
Patients who deny problem drinking may need convincing to submit to a blood draw. It may help to explain that alcohol use can exacerbate emotional problems and that the test can provide information on possible risky alcohol use.
GGT. Using a second biochemical marker may improve the sensitivity of CDT to detect heavy drinking.16-18
The most-researched choice for a second marker is gamma glutamyltransferase (GGT). Patients are considered to have tested positive for an alcohol problem if either CDT or GGT levels are elevated. Combining these tests may be especially useful in alcohol-dependent women, in whom the reliability of CDT testing alone has been questioned.
Recommendation. Start with a self-report screening measure. If the patient scores slightly below the threshold for an alcohol problem, follow up with the more costly CDT and GGT tests.
For example, biomarkers might be useful for follow-up in men with AUDIT screening scores of 6 or 7 or women with scores of 5 to 7. Biomarkers also are recommended when you suspect an alcohol problem for another reason or question whether the patient responded accurately to the self-report measure.
Screening for problem drinking: the Alcohol Use Disorders Identification Test (AUDIT)
- How often do you have a drink containing alcohol?
- How many drinks containing alcohol do you have on a typical day when you are drinking?
- How often do you have 6 or more drinks on one occasion?
- How often during the last year have you found that you were not able to stop drinking once you had started?
- How often during the last year have you failed to do what was normally expected from you because of drinking?
- How often during the last year have you needed a first drink in the morning to get yourself going after a heavy drinking session?
- How often during the last year have you had a feeling of guilt or remorse after drinking?
- How often during the last year have you been unable to remember what happened the night before because you had been drinking?
- Have you or someone else been injured as a result of your drinking?
- Has a relative, friend, doctor, or other health worker been concerned about your drinking or suggested that you cut down?
The World Health Organization offers a manual on how to administer and interpret AUDIT (http://www.who.int/substance_abuse/pubs_alcohol.htm).
Source: World Health Organization
Table 2
Biochemical markers of heavy drinking
| Marker | Time needed for return to normal limits | Level of drinking characterized | Comments |
|---|---|---|---|
| Gamma glutamyltransferase (GGT) | 2 to 6 weeks of abstinence | ~70 drinks/wk for several weeks | Most common and reliable of the traditional markers of heavy drinking; many sources of false positives |
| Aspartate aminotransferase (AST) (formerly SGOT) | 7 days, but much variability in declines with abstinence | Unknown, but heavy | Present in many organs; many sources of false positives; moderate correlations with GGT |
| Alanine aminotransferase (ALT) (formerly SGPT) | Unknown | Unknown, but heavy | Many sources of false positives and less sensitive than AST; ratio of AST to ALT may be more accurate |
| Macrocytic volume (MCV) | Unknown; half-life ~40 days | Unknown, but regular and heavy | Poor sensitivity and specificity; even with abstinence, very slow return to normal limits and may increase at first; little, if any, gender effect |
| Carbohydrate-deficient transferrin (CDT) | 2 to 4 weeks of abstinence | >60 grams/day for approximately 2 weeks | Few sources of false positives; excellent indicator of relapse |
MONITORING PATIENTS IN TREATMENT
MET. Motivational enhancement therapy (MET) has gained popularity as a means of changing problematic drinking.19 Project MATCH—a multi-site trial on alcohol abuse treatment—studied MET and two other interventions. MET required fewer sessions but equaled the other interventions in reducing drinking days and aver-age amount of alcohol consumed.20
A key component of MET—and other brief interventions—is to provide patients with empathetic, nonjudgmental feedback.19-21 Responses to the first three AUDIT items can provide such feedback to patients with drinking problems. Amazingly, heavy drinkers and alcoholics often do not realize how much more they drink than other people. To help them develop this insight, show them their self-report responses in contrast with national normative data.
Biomarker results can be used similarly, in this case comparing the patient’s score with the test’s reference range values. Kristenson et al22 showed that giving men with elevated scores recurrent biomarker information and advice significantly reduced morbidity and mortality and improved their work performance.