The Validity and Utility of a Single, Five-Colour Flow Cytometry Tube in Detecting Plasma Cell Dyscrasias at a Resource-Constrained Laboratory

Introduction: Cost is a major limitation to the utilisation of flow cytometry in resource-poor settings. This study aimed to assess the validity and utility of a single, five-colour immunophenotyping tube, employing dried monoclonal reagents instead of conventional liquid monoclonal reagents, as a tool for the diagnosis of plasma cell malignancies.

Methods: Immunophenotyping results of 26 suspected plasma cell malignancies were compared prospectively using a single customised dried monoclonal reagent tube and the current conventional liquid monoclonal reagent panel.  

Results: Cell availability, plasma cell enumeration and monoclonal antigen expression were all comparable except in the expression of the common leucocyte antigen, which was attributed to increased numbers of unlysed red cells on liquid reagent analyses. Mean fluorescence intensity was brighter on the dried monoclonal tube analyses enabling easier identification and characterisation of plasma cells. The final diagnoses obtained correlated in 92% of cases, confirming a sensitivity and specificity of 95% and 86% respectively for the dried monoclonal tube. Total processing time was 38% shorter and costs were 76% lower for the dried monoclonal tube.  

Conclusions: This single, dried monoclonal reagent tube showed a high sensitivity and specificity compared to the current reference standard, with potential cost and time- saving benefits. Laboratory verification and implementation of this novel plasma cell dyscrasia tube can be recommended in resource-constrained settings once these dried reagents are commercially validated for clinical use.