Estimation of the allowable total error of the absolute CD34+ cell count by flow cytometry using data from UK NEQAS exercises 2004-2024.

Objectives: The knowledge of the measurement uncertainty (MU) of a diagnostic laboratory test is essential to keep the reliability of laboratory results under control, is requested by regulatory bodies, and for the clinician to be aware of the grey zone of variability around the reported values. The calculation of the percent allowable total error (%aTE) defines the levels of acceptable and optimal MU for each measurand. The CD34+ hemopoietic precursor cell level in blood, as a flow cytometric measurand, still lacks reliable MU and %aTE indicators.