Principal component analysis yields results comparable to those of an elaborate Boolean strategy: simplifying the assessment of measurable residual disease in chronic lymphocytic leukemia patients

Introduction: Measurable residual disease (MRD) is becoming increasingly important in the chronic lymphocytic leukemia (CLL) context. It is of independent prognostic significance in terms of favorable progres-sion-free and overall survival. The standardized methods used to assess CLL MRD are based on flow cytometry and real-time quantitative PCR. We here present a nine-color assay for CLL MRD with the ROR-1 marker antigen as recommended by the European Research Initiative (ERIC) on CLL; the sensitivity is at least 10-5. Materials and methods: We used 54 samples to develop a new principal component analysis (PCA) method based on the Kaluza (c) "radar" presentation mode. We used a Navios flow cytometer (Beckman Coulter (c)). Results: We confirmed the linearity of our method over more than five dilutions. The specificity limit was 1.3x10-6 and the lower limit of detection was 3.6x10-6. Compared to the Boolean method, the sensitivity, specificity, and positive and negative predictive values of our PCA method were 100%. When MRD was detectable, PCA and Boolean assays were in agreement (linear regression, R2 = 0.99). Conclusion: We developed a new PCA-based method for detection of CLL MRD. Our method is comparable to that of the consensus method in terms of sensitivity, and it is also much easier and faster.