Comparative analysis between cytomorphology and flow cytometry methods in central nervous system infiltration assessment in oncohematological patients

Flow cytometry for meningeal infiltration in B acute lymphoblastic leukemia in a low middle income country

Meningeal infiltration in children with B acute lymphoblastic leukemia is one of the most serious complications. Timely diagnosis not only significantly enhances treatment efficacy but also leads to improve patient outcome and reduce risk of relapse. This is particularly crucial in low to middle income countries facing health constraints, where optimizing resources is essential. Conventional cytology (CC) study of cerebrospinal fluid (CSF) is considered in different countries to be the Gold-standard despite its low sensitivity (< 50%). The study of CSF by multiparametric flow cytometry (MFC) appears to be an alternative. The aim of our study was to assess MFC analytical performance compared with CC. Our cross sectional study was conducted over a six-month period in the biological hematology department. CSF samples underwent analysis for the presence of blasts using both CC and MFC. Cytological slides of the CSF were prepared by cytocentrifugation in a Shandon Cytospin 4™. Flow cytometric analysis was performed on the BD FACSLyric™ flow cytometer. All statistical analyses were performed using SPSS version 21.0 (SPSS Inc.). Agreement between the two methods was made using the Kappa index and χ2 test. This study was approved by the local ethics committee. Sixty CSF samples from 39 children with B acute lymphoblastic leukemia were analyzed. Meningeal infiltration was detected respectively in 20% of cases by MFC and 5% of cases by CC, with a significant difference p = 0.006. Comparing the two methods, the Kappa coefficient was 0.35, indicating weak agreement between the two methods. Moreover, MFC positivity was higher even for hypocellular samples. Of the 51 hypocellular samples, eight were positive by MFC while they were negative by CC. MFC shows better sensitivity while retaining good specificity for the detection of meningeal involvement. MFC could therefore be a complementary method to CC for detecting blast cells in the central nervous system.

Initial and follow-up evaluations on cerebrospinal fluid involvement by hematologic malignancy

Central nervous system (CNS) involvement is a serious complication in hematologic malignancy, and early detection and management of CNS involvement in these cases significantly impact the prognosis. Currently, there is no consensus on the use of multiparametric flow cytometry (MFC) and conventional cytology (CC) testing for initial and follow-up cerebrospinal fluid (CSF) specimens to diagnose CNS involvement by hematologic malignancy. In our institution, after initial MFC and CC, two subsequent negative MFCs are required before discontinuing MFC. The aim of this study is to evaluate the outcome of this approach. CSF cytology and MFC reports were retrieved from Laboratory Information System, and data was reviewed. Between January 2020 and December 2021, 1789 CSF samples from 280 patients were submitted for CSF analysis. For those 517 CSF samples tested by both MFC and CC, 97 cases tested positive by both MFC and CC with 95% concordance. Eighteen cases were MFC + /CC - and 7 were MFC - /CC + . Thirty-six cases had initially positive MFCs followed by more than one MFC evaluation. Among those 36 cases, 22 cases (61.1%) converted to negative after the second follow-up sample, 9 cases (25%) were continuously positive for at least three samples, and 5 cases (13.9%) exhibited negative to positive conversion. Compared to negative CSF cases, positive CSFs had higher total nucleated cell count and higher total protein levels while red blood cells, glucose, and lactate dehydrogenase levels remained at comparable levels. The concordance between MFC and CC was excellent. The high incidence of positive MFCs on two or more follow-up samples and the high frequency of negative MFC to positive conversion indicate the necessity of repeated negative MFCs before discontinuing MFC. The fact that more than half of the positive cases converted to negative after the second CSF specimen and most follow-up positive cases can be detected by CC alone suggests it is adequate to use CC alone for follow-up CSF study after two consecutive negative MFCs.