Use of filter paper to measure alcohol biomarkers among opioid-dependent patients on agonist maintenance treatment: A community-based study

Background: Harmful Alcohol use is frequent among opioid dependents patients undergoing agonist maintenance treatment. The objective assessment of harmful alcohol use can be done using laboratory measures of serum biomarkers. For community-based patients, there is often a requirement of an alternative method due to lack of onsite laboratory services. The aim of the study was to examine filter paper as a matrix to measure serum biomarkers of harmful alcohol use. Methods: The initial phase involved standardization of the filter-paper-based assay. Conditions were optimised for extraction and estimation of alcohol biomarkers (Aspartate Aminotransferase; AST, Alanine Aminotransferase; ALT, Gamma Glutamyl transferase; GGT and Carbohydrate Deficient Transferrin; CDT) from the filter paper. For clinical validation, serum samples were collected from community clinics. Biomarker levels obtained from both the methods were correlated using linear regression analysis. Limits of agreement between the two methods was estimated using the Intraclass Correlation Coefficient (ICC). Results: The extraction of enzymes (AST, ALT and GGT) from filter paper was carried out using the substrate buffer available with the reagent kit (Randox, UK). CDT was readily extracted from filter paper using deionised water. Serum biomarker levels measured from samples collected from community clinics correlated well with filter paper extracted levels (ICC 0.97-0.99). More than 90% of alcohol biomarker levels were recovered from the filter paper matrix using this method. Conclusion: Filter paper has the potential to be used as a matrix to objectively measure alcohol biomarkers among opioid-dependent patients from community settings lacking onsite laboratory facilities.