Value of cerebrospinal fluid white cell count and protein level in predicting leptomeningeal involvement by systemic aggressive B-cell lymphoma.

INTRODUCTION: Diagnostic cerebrospinal fluid (CSF) analysis for patients with newly diagnosed aggressive B-cell lymphoma at risk of secondary central nervous system involvement typically includes multiparametric flow cytometry (MFC), cytology (CC), white cell count (WCC) and total protein. The strength of relationships between MFC results and the remaining variables has been disputed in small studies. We explored these relationships in a large homogeneous cohort of patient samples, aiming to establish the relationship between WCC and protein level and MFC results. METHODS: Adult patients with aggressive B-cell lymphoma at risk of CNS involvement who underwent staging CSF analysis by MFC were identified retrospectively from institutional electronic records between October 2011 and December 2020. RESULTS: Three hundred and seventy eight samples, including 45 (11.9%) MFC+ samples, were analysed. The relative sensitivity of CC for MFC positivity was 0.38, with PPV of 0.68. Significantly higher median WCC (p < .001) and protein levels (p = .011) were seen in MFC+ vs. MFC- samples. MFC + CC+ (vs. MFC + CC- samples) demonstrated higher median neoplastic events and neoplastic cell concentration. WCC ≥36 × 106 /L and protein ≥1.12 g/L cut-off values demonstrated the highest PPVs for MFC positivity (0.67 and 0.88, respectively). CONCLUSIONS: Statistically significant associations exist between elevated WCC and protein and MFC positivity, and selected WCC and protein cut-off values have PPVs comparable to that of cytological assessment. Whilst routine WCC and protein analysis may be unnecessary, WCC/protein values above these levels could be regarded as reasonable evidence of CSF involvement in the appropriate setting.

Myeloblasts in normal bone marrows expressing leukaemia-associated immunophenotypes.

Measurable residual disease (MRD) status of patients undergoing treatment for acute myeloid leukaemia (AML) is important for prognosis and guides treatment. Multicolour flow cytometry (MCF) is a sensitive MRD method. The current approach relies on identification of blasts expressing leukaemia-associated immunophenotypes (LAIP) or by blasts expressing aberrant differentiation/maturation profiles compared to that seen in normal haematopoietic precursor cells at follow-up, i.e., different from normal (DFN). However, expression of LAIP on normal myeloblasts affects the specificity of the result, and the understanding of what is normal is important. Limited published data are currently available. We report findings from 14 normal adult bone marrows. MCF was performed on the residual normal marrow specimens from 14 adults. Expression of CD15, CD11b, CD7, CD4, and CD56 on CD34+ myeloblasts was assessed. Analysis of samples was performed using 4-colour flow cytometry which was the methodology used when this work was done, and is still being used in many clinical flow laboratories worldwide. LAIP is defined by lineage infidelity or asynchronous expression of differentiation markers. The cases of normal myeloblasts with LAIP involving the markers used and above the cut-off levels for MRD detection (0.01%) varies between 43% and 100%, limiting the specificity of the results for MRD. Even if the threshold is raised to 0.1%, there will still be false positive cases using aberrant CD15 or CD7. Our work provided useful information for AML MRD determination in our laboratory. A collaborative database of LAIP on normal myeloblasts using standardised analysis should be useful to determine the optimal diagnostic cut-off for AML MRD using LAIP.

Early treatment of acute promyelocytic leukaemia is accurately guided by the PML protein localisation pattern: real-life experience from a tertiary New Zealand centre.

Current guidelines recommend that a rapid test be used to assist diagnosis of acute promyelocytic leukaemia (APL), but the choice of an assay is discretionary. PML immunofluorescence (PML IF) identifies the microparticulate pattern of the PML protein localisation, highly specific for APL. The aim of this study was to evaluate clinical utility of PML IF in a real-life setting based on a retrospective records review for all patients who had PML IF performed in our centre between 2000 and 2017. Final analysis included 151 patients, 70 of whom had APL. PML IF was reported on average 3 days faster than cytogenetics. Compared with genetic results, PML IF showed sensitivity of 96% and specificity of 100%. PML IF accurately predicted APL in four APL cases with cryptic karyotype/FISH and excluded APL in 98% cases tested based on the suspicious immunophenotype alone, 21/28 of whom had mutated NPM1. Results of PML IF influenced decision to start ATRA in 25 (36%) APL patients and led to its termination in six non-APL patients. In conclusion, PML IF is a fast and reliable test that facilitates accurate treatment decisions when APL is suspected. This performance of PML IF remains hard to match in a real-life setting.