Validation of an Optimized <scp>DuraClone</scp> Phenotyping Kit Workflow for <scp>TBNK</scp> Subset Quantification

Quantification of T-cells, B-cells, and NK-cells assay is crucial for diagnosing and monitoring immune diseases and evaluating lymphodepleting therapies. To standardize and validate an optimized workflow of the Beckman Coulter DuraClone IM Phenotyping Basic Kit for quantification of TBNK subsets in peripheral blood. Procedural changes included the use of an alternative lysis buffer, the addition of counting beads, the elimination of centrifugation steps, and an increase in acquisition volume. Validation followed CLSI H42-A2 and H62 guidelines, assessing accuracy, precision, linearity, and limit of quantification (LLOQ). Accuracy was evaluated by comparison with Immuno-Trol controls and by Bland-Altman analysis against standard immunophenotyping methods. External proficiency was assessed through participation in the College of American Pathologists (CAP) TBNK program in 2024. Procedural steps were reduced by 50%, and processing time by 38.6%. The modified method demonstrated high accuracy (-3 < bias < 35; cells/μL), a low bias based on Immuno-Trol targets, and strong agreement in the Bland-Altman analysis. The method successfully passed three CAP external proficiency tests in 2024, confirming interlaboratory reliability. Coefficients of variation for precision were below 10% for all subsets. Linearity exceeded R ² > 0.99 across clinically relevant ranges. Most subsets demonstrated an LLOQ below 10-50 cells/μL, which is suitable for clinical applications. The proposed modifications to the DuraClone IM kit protocol improved workflow efficiency and analytical performance without compromising accuracy or reproducibility. The validated method provides a standardized, reliable, and time-efficient alternative for lymphocyte subset quantification.