Carbohydrate-deficient transferrin test

Current Psychiatry. 2005 June;04(06):80-87

June 1, 2005|Psychiatry

Peter M. Miller, PhD;Cynthia Dominick, MHA;Raymond F. Anton, MD

A tool for detecting alcohol abuse

Overall, %CDT is as sensitive as GGT and more sensitive than other biomarkers, including MCV, aspartate transaminase, and alanine transaminase.⁹ %CDT is more specific than GGT (92% vs. 75%) and other biomarkers. %CDT appears to be more sensitive in men, whereas GGT is more sensitive in women (Table 2).¹⁰

Ample evidence, however, suggests that %CDT and GGT readings together may provide a comprehensive picture of recent alcohol abuse.¹⁰ Whereas frequent drinking alters %CDT, GGT signals drinking intensity and is more effective at detecting episodic binge drinking (Table 2). This probably explains why problem drinkers age <20—who typically binge-drink—show little or no change in %CDT.

Table 2

%CDT vs GGT testing for recent alcohol abuse

	%CDT	GGT
Advantages	High specificity Unaffected by common medications Unaffected by most medical conditions Good indication of relapse Normalizes within 2 weeks of abstinence	As sensitive as %CDT with severe alcoholics More accurate in women Currently available in more clinical labs Sensitivity is additive to %CDT
Disadvantages	Affected by end-stage liver disease, biliary cirrhosis and rare transferrin variant Not as accurate in women and binge drinkers	Affected by liver disease, obesity, anticonvulsant medications, hormone supplements, histamine blockers More false positives than %CDT
Cutoff value	2.6%	54 μ/L
%CDT: Carbohydrate-deficient transferrin percentage
GGT: Gamma-glutamyltransferase

FACTORS THAT ALTER RESULTS

Unlike GGT and MCV, few medical conditions distort %CDT,¹¹ meaning the test is accurate in patients with most medical conditions. Only end-stage liver disease, biliary cirrhosis, and rare genetic transferrin variants alter %CDT.

Women tend to have higher and more-variable CDT values than do men, possibly because of variability in normal transferrin levels, anemia secondary to iron deficiency, pregnancy, use of oral contraceptives, or menopause. %CDT cutoff scores are not gender-specific, however, because percentage rather than absolute CDT is typically measured.

%CDT seems to decrease slightly as body mass index increases, suggesting a small but significant inverse relationship between weight and %CDT. Smoking seems to raise %CDT values slightly. The specifics of and reasons for these relationships are unclear.

Related resources

Axis-Shield. www.axis-shield.com. Click on “Lab diagnostics,” then “Alcohol-related.”

Disclosure

Dr. Anton is a consultant to Axis-Shield.

Dr. Miller and Ms. Dominick report no financial relationship with any company whose products are mentioned in this article, or with manufacturers of competing products.

References

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