An international panel’s efforts to achieve standardization for the biomarker of alcohol consumption, carbohydrate-deficient transferrin (CDT), have progressed to the point of fully validating the candidate reference measurement procedure (cRMP) to make it an accepted RMP. This means CDT standardization is at hand.
“The achieved standardisation and introduction of a common unique identifier for standardised CDT measurements allows for direct comparison of values obtained by different routine measurement procedures, and use of a common reference interval,” the panel wrote. “This will improve the diagnostic performance of CDT measurement as a biomarker of chronic heavy/excessive alcohol consumption, advance the ability to compare clinical and analytical trials on CDT, and last, but not least, improve patient care.”
In a report published in Clinica Chimica Acta, the International Federation of Clinical Chemistry and Laboratory Medicine Working Group on Standardisation of Carbohydrate-Deficient Transferrin updated its work since 2005 in achieving standardization for CDT measurement.
CDT has been proposed as a better marker of sustained moderate to high alcohol consumption than traditional measures such as liver function tests and the mean corpuscular volume of erythrocytes (MCV). However CDT testing has been less than optimal, because different methods cover variable fractions of the transferrin glycoforms normally present in blood and because there are a wide variety of method-dependent cut-off values. In addition, test results are expressed as either absolute (e.g., mg/L or U/L) or relative (e.g., the percentage of total transferrin or of disialotransferrin).
In its decade-long effort to achieve standardized CDT measurement, the working group defined as the measurand serum disialotransferrin to total transferring fraction expressed in percentage. The group also selected and fully validated a cRMP for CDT, based on high-performance liquid chromatography with spectrophotometric detection. An international network of labs subsequently used the cRMP to assess between-lab reproducibility, establish a reference interval, and develop a reference material based on human serum.
The work of the CDT reference labs established 1.7% as the upper limit of the reference interval for the disialotransferrin to total transferrin fraction. This was based on the mean value plus 2 standard deviations for healthy controls, and the 97.5 percentile for non-drinkers and light/heavy drinkers combined.