Cross-sectional reassessment after 4 years of clinical routine use of AQUIOS CL for absolute T cell quantitation in a university hospital.

Background: We had previously reported appropriate performances of automated AQUIOS CL cytometer (Beckman Coulter) for regulatory approval of absolute T cell enumeration. However, after 4 years of routine use, we still observed recurrent histogram anomalies that may affect both absolute values and T cell subset percentages results. The objective of the current study was thus to perform a cross-sectional evaluation of these graphical anomalies within a university hospital context, to assess their influence on results and ultimately to propose a standardized decision tree to circumvent graphical disturbances at the time of results validation.

Methods: Eight hundred and sixty-two blood samples were prospectively analyzed on AQUIOS CL. Results were compared to (i) lymphocyte values from complete blood count; (ii) results from manual staining and analysis on Navios cytometer (Beckman Coulter); (iii) results after washing step and reacquisition on AQUIOS CL.

Results: Nearly 75% analyses did not show any graphical anomaly. 20% had single anomaly on "Lymphs (45)" or "Lymphs EV" regions influencing T cells percentages and requiring manual re-gating of "CD3- capture" region. 5% showed concomitant "Lymphs EV" and "Lymphs (45)" anomalies influencing both T cell percentages and absolute counting and requiring additional staining and analysis on Navios. Finally, <1% presented with anomaly on "CD4/CD8" histogram or "CD3+ All" region, influencing both T cell percentages and absolute counting.

Conclusions: Around 25% AQUIOS CL results were flawed due to gating anomalies. In <5% cases, additional back-up procedures should be undertaken to ensure results validity. A simple decision-tree may help in guiding validation process.