Diagnostic performance and heterogeneity of validated flow cytometry scores: a systematic review

values were consistently high for sensitivity and, in two cases, also for specificity, indicating high heterogeneity. To explain this variability, we systematically reviewed study methods and identified 31 potential sources of heterogeneity, spanning study design, pre-analytical, analytical, and post-analytical factors. In conclusion, few flow cytometry scores have been validated, most only in limited cohorts, and their reported diagnostic performance varies widely. While numerous potential sources of variability can be identified, the small number of available studies prevents reliable quantification of their impact. Published accuracy estimates should therefore not be accepted at face value, and proposed scores should be validated in-house before being adopted into diagnostic practice.