Standardization of the capillary electrophoresis procedures Capillarys® CDT and Minicap® CDT in comparison to the IFCC reference measurement procedure.

CDT is at present the most relevant routinely available biological marker of alcohol use and is widely used for screening and monitoring of patients. The lack of standardization leads to specific reference intervals for each procedure. The IFCC working group devoted to CDT demonstrated that the standardization is possible using calibrators assigned to the reference measurement procedure. In this study, we compare the capillary electrophoresis (CE) techniques Capillarys® CDT and Minicap® CDT (Sebia, Lisses, France) to the reference procedure before and after standardization in 126 samples covering the range of CDT measurement. Both capillary electrophoresis procedures show a high correlation (r=0,997) with the reference procedure and the concordance correlation coefficient evaluated according to Mc Bride is "almost perfect" (>0.997 for both CE procedures). The number of results with a relative difference higher than the acceptable difference limit is only 1 for Capillarys® CDT and 5 for Minicap® CDT. These results demonstrate the efficiency of the standardization of CDT measurements for both CE techniques from Sebia, achieved using calibrators assigned to the reference measurement procedure.

Reprint of Standardisation and use of the alcohol biomarker carbohydrate-deficient transferrin (CDT).

Carbohydrate-deficient transferrin (CDT) is a glycoform profile of serum transferrin that increases in response to sustained high alcohol intake and over the last decades has become an important alcohol biomarker with clinical and forensic applications. However, the wide range of CDT measurement procedures has resulted in lack of uniform results and reference limits, and hampered comparison of results. In 2005, the IFCC therefore founded a special working group (WG) aiming for standardisation of CDT measurement. This review summarises the history of CDT and the actions taken by the WG-CDT. Initial steps included the definition of the measurand (serum disialotransferrin to total transferrin fraction expressed in %), and the determination of a well-defined anion-exchange HPLC procedure as the candidate reference measurement procedure (cRMP). Subsequent achievements were the establishment of a network of reference laboratories to perform the cRMP, setting a reference interval, and development of a reference material based on human serum for which the laboratory network assign values. Using a set of reference materials for calibration allowed for achieving equivalence of results of all present CDT measurement procedures. The final steps of the WG-CDT have been a full validation of the cRMP to make it an IFCC approved RMP, and providing guidance for international standardisation of all CDT measurement procedures.

IFCC approved HPLC reference measurement procedure for the alcohol consumption biomarker carbohydrate-deficient transferrin (CDT): Its validation and use.

Carbohydrate-deficient transferrin (CDT) is used as a biomarker of sustained high alcohol consumption. The currently available measurement procedures for CDT are based on various analytical techniques (HPLC, capillary electrophoresis, nephelometry), some differing in the definition of the analyte and using different reference intervals and cut-off values. The Working Group on Standardization of CDT (WG-CDT), initiated by the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC), has validated an HPLC candidate reference measurement procedure (cRMP) for CDT (% disialotransferrin to total transferrin based on peak areas), demonstrating that it is suitable as a reference measurement procedure (RMP) for CDT. Presented is a detailed description of the cRMP and its calibration. Practical aspects on how to treat genetic variant and so-called di-tri bridge samples are described. Results of method performance characteristics, as demanded by ISO 15189 and ISO 15193, are given, as well as the reference interval and measurement uncertainty and how to deal with that in routine use. The correlation of the cRMP with commercial CDT procedures and the performance of the cRMP in a network of laboratories are also presented. The performance of the CDT cRMP in combination with previously developed commutable calibrators allows for standardization of the currently available commercial measurement procedures for CDT. The cRMP has recently been approved by the IFCC and will be from now on be known as the IFCC-RMP for CDT, while CDT results standardized according to this RMP should be indicated as CDTIFCC.

Discovery of a gamma heavy chain disease in a patient followed-up for a lymphoplasma cell proliferative disorder.

Gamma-heavy chains disease is a rare disease, with very few cases described in the literature. It is characterized by the presence of a monoclonal gamma-heavy chain without associated light chain. Its prevalence and prognosis are unknown. We report here the accidental discovery of a case of gamma-heavy chain disease during a pancytopenia exploration, performed in the hospital, in a patient known since 2002 for a lymphoplasmacytic type lymphoma first localized in bone marrow.

Standardisation and use of the alcohol biomarker carbohydrate-deficient transferrin (CDT).

Carbohydrate-deficient transferrin (CDT) is a glycoform profile of serum transferrin that increases in response to sustained high alcohol intake and over the last decades has become an important alcohol biomarker with clinical and forensic applications. However, the wide range of CDT measurement procedures has resulted in lack of uniform results and reference limits, and hampered comparison of results. In 2005, the IFCC therefore founded a special working group (WG) aiming for standardisation of CDT measurement. This review summarises the history of CDT and the actions taken by the WG-CDT. Initial steps included the definition of the measurand (serum disialotransferrin to total transferrin fraction expressed in %), and the determination of a well-defined anion-exchange HPLC procedure as the candidate reference measurement procedure (cRMP). Subsequent achievements were the establishment of a network of reference laboratories to perform the cRMP, setting a reference interval, and development of a reference material based on human serum for which the laboratory network assign values. Using a set of reference materials for calibration allowed for achieving equivalence of results of all present CDT measurement procedures. The final steps of the WG-CDT have been a full validation of the cRMP to make it an IFCC approved RMP, and providing guidance for international standardisation of all CDT measurement procedures.

Head-to-head comparison of 10 natriuretic peptide assays.

BACKGROUND: The aim of the study was to compare NT-proBNP and BNP levels in fresh samples from heart failure (HF) patients measured using 10 immunoassays and to assess their agreement. METHODS: NT-proBNP (CobasH232(®), Elecsys(®), Vidas(®), Vista(®), XPand(®), Vitros(®)) and BNP (Triage(®), Access(®), CentaurXP(®), Architect(®)) levels were measured in 39 heparin and 19 EDTA samples, respectively. RESULTS: The Pearson correlation coefficient ranged between 0.929 (Triage(®-)Centaur(®)) and 0.994 (Access(®)-Architect(®)) for BNP assays and between 0.972 (Vidas(®)-Cobas H232(®)) and 0.999 (Vitros(®)-Vidas(®)) for NT-proBNP assays. Passing Bablok regression analyses showed a significant difference in the slopes [0.80 (Centaur(®)-Triage(®)) to 1.84 (Architect(®)-Centaur(®))] and intercepts [-55 ng/L (Architect(®)-Centaur(®)) to 48 ng/L (Access(®)-Triage®)] for BNP assays, and a lower heterogeneity between NT-proBNP assays [0.83 (Vidas(®)-Elecsys(®)) to 1.20 (Vitros(®)-Vidas(®)) and -97 ng/L (XPand(®)-CobasH232(®)) to 51 ng/L (CobasH232(®)-Elecsys(®)) for slopes and intercepts, respectively]. The concordance correlation coefficient revealed a poor (ρc<0.90) to moderate (ρc=0.90-0.95) agreement in 4/6 pairs of BNP assays and an almost perfect (ρc>0.99) agreement in 5/15 pairs of NT-proBNP assays. The acceptable difference limit reflecting the number of individual discrepant results between two assays, ranged between 15.1% (Access(®)-CentaurXP(®)) and 34.5% (Architect(®)-Triage(®)) for BNP assays, and between 10.9% (Vidas(®)-Vitros(®)) and 55% (CobasH232(®)-Xpand(®)) for NT-proBNP assays. CONCLUSIONS: This study stresses the lack of transferability of the results obtained using different techniques to measure BNP and NT-proBNP levels in fresh samples. Individual reference ranges and HF diagnostic cut-offs should be assessed for each commercial NP immunoassay. We recommend to systematically monitoring HF patients using the same assay (BNP or NT-proBNP) over the time.

Harmonization of measurement results of the alcohol biomarker carbohydrate-deficient transferrin by use of the toolbox of technical procedures of the International Consortium for Harmonization of Clinical Laboratory Results.

BACKGROUND: The need for equivalent results of routine measurement procedures for the alcohol biomarker carbohydrate-deficient transferrin (CDT) has been recognized by the IFCC. This article describes a project to harmonize CDT as conducted by an IFCC working group initiated for this purpose. METHODS: We used procedures for achieving harmonization as developed by the Consortium for Harmonization of Clinical Laboratory Results to assess the suitability of a candidate reference measurement procedure (cRMP), candidate reference materials (cRMs), and the success of efforts to achieve harmonization. RESULTS: CDT measurement procedures in routine use showed good reproducibility (CV 1.1%-2.8%) and linearity (r > 0.990) with variable slopes (0.766-1.065) and intercepts (-0.34 to 0.92) compared to the cRMP. Heterogeneity after simulated harmonization was 4.7%. cRMs of frozen human native sera demonstrated commutability and 3-year stability for routine measurement procedures. The cRMP provided reproducible value assignment to cRMs with an expanded uncertainty (k = 2) of 0.03% at the 1.2% CDT level and 0.06% at the 4.4% CDT level. Harmonization efforts reduced the intermeasurement CV from 8.8% to 3.4%, allowed 99% recovery of the values assigned with the cRMP, and demonstrated 99% of results within the desirable allowable total error. Harmonization was less successful in samples with low CDT and high trisialotransferrin concentrations. CONCLUSIONS: Harmonization of CDT is possible with frozen human native sera as cRMs with values assigned by use of the cRMP. We propose the cRMP as a candidate international conventional reference measurement procedure and cRMs as candidate international calibrators.

Toward standardization of carbohydrate-deficient transferrin (CDT) measurements: III. Performance of native serum and serum spiked with disialotransferrin proves that harmonization of CDT assays is possible.

Carbohydrate-deficient transferrin (CDT) is a generic term that refers to the transferrin glycoforms whose concentration in blood is temporarily increased by sustained alcohol consumption. Due to high clinical specificity, CDT was proposed as a biomarker of heavy alcohol use and has been available for about 20 years. A number of methods have been developed for CDT measurement based on different analytical techniques and principles and without any harmonization or calibration to a reference method. As a consequence, neither the reference limits nor the cut-off values have been similar across assays, hampering understanding of the diagnostic value of CDT and its routine use. This prompted the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) to initiate a Working Group on Standardization of CDT (WG-CDT). This third publication of the WG-CDT is devoted to testing the commutability of native and disialotransferrin-spiked serum panels as candidate secondary reference materials, in order to prove the harmonization potential of commercial CDT methods. The results showed that assay harmonization reduced the inter-laboratory imprecision in a network of reference laboratories running the HPLC candidate reference method. In the seven commercial methods evaluated in this study, the use of multi-level secondary calibrators of human serum origin significantly reduced the between-method imprecision. Thus, harmonization of CDT measurements by different methods can be achieved using this calibration system, opening the way for a full standardization of commercial methods against a reference method by use of certified reference materials.

[Inventory of the use of natriuretic peptides in France]. / État des lieux de l'utilisation des peptides natriurétiques en France.

Since the introduction of routine assay for natriuretic peptides (NP), there is an increasing number of clinical applications for these assays. Due to the continuously increasing number of prescription of those tests, a reappraisal of the use of natriuretic peptide assays, namely BNP and NT-proBNP in France was necessary. This was achieved through a national survey to obtain a detailed description of NP prescription and realization by French laboratories. A questionnaire was sent in April 2010 to hospital and private clinical chemists. Statistical analysis of results concerned 584 answers. This survey demonstrated an equivalent use of BNP and NT-proBNP both in public or private laboratories together with a huge heterogeneity of tests used within labs. Medical prescription heterogeneity both in public or private sectors confirms the large implication of those tests in clinical diagnosis. These assays are not yet standardized, so clinicians and biologists should be very careful when interpreting the results for diagnostic or therapeutic monitoring.

Toward standardization of carbohydrate-deficient transferrin (CDT) measurements: II. Performance of a laboratory network running the HPLC candidate reference measurement procedure and evaluation of a candidate reference material.

Carbohydrate-deficient transferrin (CDT) is a descriptive term used for a temporary change in the transferrin glycosylation profile caused by alcohol, and used as a biomarker of chronic high alcohol consumption. The use of an array of methods for measurement of CDT in various absolute or relative amounts, and sometimes covering different transferrin glycoforms, has complicated the comparability of results and caused confusion among medical staff. This situation prompted initiation of an IFCC Working Group on CDT standardization. This second publication of the WG-CDT covers the establishment of a network of reference laboratories running a high-performance liquid chromatography (HPLC) candidate reference measurement procedure, and evaluation of candidate secondary reference materials. The network laboratories demonstrated good and reproducible performance and thus can be used to assign target values for calibrators and controls. A candidate secondary reference material based on native human serum lyophilized with a cryo-/lyoprotectant to prevent protein denaturation was found to be commutable and stable during storage. A proposed strategy for calibration of different CDT methods is also presented. In an external quality assurance study involving 66 laboratories and covering the current routine CDT assays (HPLC, capillary electrophoresis and immunoassay), recalculation of observed results based on the nominal values for the candidate calibrator reduced the overall coefficient of variation from 18.9% to 5.5%. The logistics for distribution of reference materials and review of results were found to be functional, indicating that a full reference system for CDT may soon be available.

Evaluation of capillary electrophoresis assay for CDT on SEBIA's Capillarys System: intra and inter laboratory precision, reference interval and cut-off.

BACKGROUND: Carbohydrate-deficient transferrin (CDT) measurement on the multicapillary system Capillarys™ is characterized by high throughput and an on-line sample pre-treatment. This study evaluates the linearity and the precision of this technique, the correlation with the candidate reference method and the effect of genetic transferrin variants. Upper reference limit and cut-off values were calculated. METHODS: The precision study was carried out following CLSI EP5-A protocol. The between laboratory variation was calculated from an eight-site study. The upper reference limit (URL) was conventionally calculated from a reference population of 225 samples and verified by a Bhattacharya analysis in a large (n=19,129) population. A population of 314 heavy consumers was used for calculation of the cut-off limit. Additionally the measurement uncertainty was calculated according to EDMA (European Diagnostic Manufacturers Association) and IRMM. RESULTS: The imprecision found was less than 5%, linearity was excellent for CDT values ranging from 2% to 20%. The between site variation around the cut-off value (CDT ranging from 1.68% to 1.79%) was clinically not significant. The upper reference limit (95th percentile) was calculated at 1.3% by the conventional IFCC method and confirmed by Bhattacharya calculations. The optimum cut-off for this CZE method was 1.6%, taken into account the measurement uncertainty. The regression equation with the candidate reference method was Disialotransferrin(Capillarys2)=Disialotransferrin(HPLC)∗0.968-0.248. Genetic variants and abnormal profiles were well recognized. CONCLUSIONS: These results demonstrate that the Capillarys CDT method is robust and reliable in routine use with a high degree of homogeneity from one system to another and is highly correlated with the candidate HPLC reference method.

Automated measurement of carbohydrate-deficient transferrin using the Bio-Rad %CDT by the HPLC test on a Variant HPLC system: evaluation and comparison with other routine procedures.

AIMS: In this study, we evaluated the new %CDT by the HPLC method (Bio-Rad, Germany) on a Varianttrade mark HPLC system (Bio-Rad), checked the correlation with well-known methods and calculated the diagnostic value of the test. METHODS: Intra-run and day-to-day precision values were calculated for samples with extreme serum transferrin concentrations, high trisialotransferrin and interfering conditions (haemolysed, lactescent and icteric samples). The method was compared with two routine procedures, the %CDT TIA (Bio-Rad, Hercules, CA, USA) and the Capillarystrade mark CDT (Sebia, France). A total of 350 clinical sera samples were used for a case-control study. RESULTS: Precision values were better in high CDT and medium CDT pools than in low CDT pools. The serum transferrin concentration had no effect on CDT measurement, except in samples with serum transferrin <1 g/L. Haemolysis was the only interfering situation. The method showed high correlation (r(2) > 0.95) with the two other methods (%CDT TIA and CZE %CDT). The global predictive value of the test was >0.90 at 1.9% cut-off. CONCLUSIONS: These results demonstrate that the %CDT by the HPLC test is suitable for CDT routine measurement; the results from the high-throughput Varianttrade mark system are well correlated with other methods and are of high diagnostic value.

Analytical evaluation of a new capillary electrophoresis method for carbohydrate-deficient transferrin measurement.

BACKGROUND: Carbohydrate-deficient transferrin (CDT), the sum of a- and disialotransferrin, is considered the most efficient routine biological marker of alcohol abuse. In recent years, methods based on capillary zone electrophoresis (CZE) have been developed using specialized monocapillary systems. These are characterized by a high analytical detection level, counterbalanced by a poor productivity. We evaluated a new CZE method for CDT measurement on the Sebia Capillarys, an eight-capillary system developed for routine serum capillary electrophoresis. METHODS: Precision and possible biases due to abnormal (low or high) transferrin levels or lipemic samples were assessed. Exactitude and precision were tested by comparison with a HPLC procedure acknowledged to be the most reliable to date. The validity of the manufacturer's cut-off was checked by measuring CDT in a population comprising abstaining patients, moderate alcohol consumers and alcohol abusers. Lastly, the method was compared to the routine %CDT TIA and N Latex CDT methods. RESULTS: The imprecision was 18.5% at the minimum detection level and decreased to 6.1% for high CDT values. No significant shift in the CDT results was observed in relation to abnormally low or high serum transferrin, or in lipemic samples. A high level of concordance was observed with the HPLC method used as reference. The results were strongly correlated with both other routine methods (r>0.90). The diagnostic values were comparable to the literature data, even if differences in the studied populations make difficult a direct comparison of the results. Our data suggested that the cut-off could be raised from 1.3% to 1.4% to reduce the number of false positive values without loss of diagnostic efficiency. CONCLUSIONS: This Capillarys method from Sebia showed good precision as compared to those published using other CZE methods. Capillarys method correlated well with HPLC and two routine methods. However, we noticed significant bias at low CDT concentrations. Therefore, with the advantage of high throughput and full automation, these results indicate that the new method is a consistent alternative to the other methods proposed for routine CDT measurement.

Toward standardization of carbohydrate-deficient transferrin (CDT) measurements: I. Analyte definition and proposal of a candidate reference method.

An alcohol-associated change in the serum transferrin glycoform pattern, carbohydrate-deficient transferrin (CDT), is used as a biomarker of chronic moderate to heavy alcohol consumption. A current limitation in CDT analysis is the lack of standardization, which hampers clinical and analytical comparison between studies. This situation prompted initiation of a Working Group (WG) on CDT Standardization under the auspices of the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC). The standardization work aims to define and validate the analyte, select a reference method, work out procedures for the production of reference materials, and make suggestions for the clinical usage of CDT. The first recommendation of the WG is that disialotransferrin should be the primary target molecule for CDT measurement and the single analyte on which CDT standardization is based. It is further recommended that HPLC should be the analytical principle considered as the basis of an interim reference method until a suitable mass spectrometric reference method is established. In clinical use, CDT should be expressed in a relative amount (% CDT), to compensate for variations in the total transferrin concentration.

Development and multicenter evaluation of the N latex CDT direct immunonephelometric assay for serum carbohydrate-deficient transferrin.

BACKGROUND: Carbohydrate-deficient transferrin (CDT) is a promising biomarker of alcohol abuse. We describe the development and multicenter evaluation of N Latex CDT (Dade Behring), an automated, particle-enhanced, homogeneous immunonephelometric assay for directly determining CDT. METHODS: N Latex CDT uses a monoclonal antibody that recognizes the structure of transferrin glycoforms lacking 1 or 2 complete N-glycans [i.e., disialo-, monosialo-, and asialotransferrins (CDT glycoforms)] in combination with a simultaneous assay for total transferrin. The Dade Behring BN II and BN ProSpec systems automatically calculate the CDT value as a percentage of total transferrin (%CDT). No preanalytical sample treatment is used. RESULTS: Total imprecision values for serum pools containing 1.8%-8.7% CDT were 3.4%-10.4% (mean, 6.8%). The mean (SD) %CDT for 561 serum samples from healthy control individuals was 1.76% (0.27%; range, 1.01%-2.85%). No marked sex or age differences were noted. The 97.5th percentile was at 2.35%. Transferrin genetic variants did not interfere with measurements. High transferrin concentrations did not falsely increase %CDT values, but increased %CDT values were noted for some samples with transferrin concentrations <1.1 g/L. N Latex CDT results correlated with those of a commercial CDT immunoassay involving column separation (r(2) = 0.862) and an HPLC candidate reference method (r(2) = 0.978). CONCLUSION: N Latex CDT is the first direct immunoassay for quantifying %CDT in serum. The specificity of N Latex CDT for identifying alcohol abuse may be higher than for immunoassays that use column separation, because transferrin genetic variants do not interfere with measurements.

Dose-effect relation between daily ethanol intake in the range 0-70 grams and %CDT value: validation of a cut-off value.

AIM: To evaluate the ability to infer alcohol consumption using the %CDT (carbohydrate deficient transferrin) immunoassay (Axis Shield). METHODS: One hundred and eighty-three healthy subjects (143 men, 40 women) undergoing a routine medical check-up at their workplace declared frequency and quantity of alcohol consumption covering the last 4 weeks. Seven sub-groups were made up from this population, according to daily ethanol intake and by increments of 10 g from 0 to 70 g/day. A reference group that consisted of 133 healthy teetotallers (74 men, 59 women) was recruited by occupational medicine in the same conditions as the 183 subjects of the study. Percentage CDT and gamma glutamyl transferase (GGT) were assayed on a fasting blood sample. RESULTS: There was a proportional dose-response effect of daily ethanol intake on %CDT values in the range of 0-70 g per day. A threshold effect on %CDT values for patients having an alcohol intake of over 40 g per day was found, an effect which was not observed for GGT activity. CONCLUSION: The kit has clinical usefulness, and the value of 2.6% proposed by the manufacturer for the cut-off for hazardous drinking in both sexes has been validated.

Carbohydrate-deficient transferrin and gamma-glutamyl transpeptidase in the evaluation of alcohol consumption. A five-year retrospective study of 633 outpatients in a single center.

OBJECTIVE: Carbohydrate-deficient transferrin has been proposed to be useful in evaluating alcohol consumption but there is no consensus on its use in routine practice. The aim of this retrospective study was to compare carbohydrate-deficient transferrin and gammaglutamyl transpeptidase assays for the evaluation of alcohol consumption. METHODS: Six hundred thirty-three outpatients attending one outpatient care center were included in this study. Patients were divided into five categories according to alcohol consumption: category 1 included non-weaned patients drinking more than 30 g/day for women and more than 50 g/day for men, category 2 included relapse patients, category 3 included moderate drinkers, category 4 included patients weaned less than one month, and category 5 included patients weaned more than one month. One experienced physician estimated alcohol intake from patient declarations during a face-to-face interview. RESULTS: Sensitivity of carbohydrate-deficient transferrin varied, depending on patient category, from 32% to 92% versus 41% to 72% for gamma-glutamyl transpeptidase. Specificity of carbohydrate-deficient transferrin varied from 71% to 96% versus 23% to 62% for gamma-glutamyl transpeptidase. After one month of abstinence, specificity of carbohydrate-deficient transferrin was 62% versus 19% for gamma-glutamyl transpeptidase. CONCLUSION: This study confirms that carbohydrate-deficient transferrin is more accurate in predicting alcohol consumption compared with gamma-glutamyl transpeptidase in alcoholic outpatients.

Multicenter validation study of the %CDT TIA kit in alcohol abuse and alcohol dependence.

BACKGROUND: Carbohydrate-deficient transferrin (CDT) and gamma-glutamyl transferase (GGT) are used as biomarkers of alcohol misuse. The aim of this study was to evaluate, in terms of sensitivity and specificity, the performance of the new Bio-Rad %CDT TIA kit and GGT assay for identifying alcohol abuse and alcohol dependence (according to the DSM-IV criteria). METHODS: An open multicenter study (30 centers) over 3 months, including patient groups of "abusers," "dependents," and controls, was conducted in France. RESULTS: In alcohol abuse, the sensitivity of GGT was 0.56, and that of CDT was 0.80; in alcohol dependence, the sensitivity of GGT was 0.86, and that of CDT was 0.91. The specificity of GGT was 0.77, and that of CDT was 0.83. The association of GGT with CDT increased sensitivity for alcohol abuse to 0.90 and for alcohol dependence to 0.99, but it appreciably decreased specificity (0.63). CONCLUSIONS: %CDT is the better screening marker for alcohol abuse and dependence, but GGT is still a useful marker for the detection of alcohol dependence. As an assay method, the second-generation Bio-Rad %CDT immunoassay can be recommended for routine CDT measurement.

The use of biological laboratory markers in the diagnosis of alcohol misuse: an evidence-based approach.

BACKGROUND: A large number of patients seen in clinical practice have an underlying alcohol problem. There is a pressing need for accurate methods to diagnose alcohol over-consumption objectively. Our aim was to determine how best to use biological markers to objectify alcohol problems in patients with clinical suspicion of alcohol misuse. METHODS: A 6-month longitudinal multicenter trial was conducted, using four study groups (alcohol abusers, alcohol-dependents, healthy controls and consulting controls). CDT, GGT and MCV were measured. Statistical analyses used a computer learning system that created classification systems displayed in decision trees. RESULTS: In 379 subjects the marker that best discriminated those with alcohol problems from controls was CDT. GGT then helped to differentiate between alcohol abuse and alcohol dependence in cases of high CDT. MCV, age and gender provided no extra information. DISCUSSION: We recommend CDT as a first-line biological marker to confirm or disprove suspected alcohol misuse. High CDT plus GGT above normal points to alcohol dependence, while high CDT plus GGT below normal is evidence of alcohol abuse.