Flow cytometry and cytomorphology evaluation of hematologic malignancy in cerebrospinal fluids: comparison with retrospective clinical outcome

An independent clinical assessment was compared with flow cytometry (FCM) and cytomorphology results obtained on 227 cerebrospinal fluids investigated for hematologic malignancy, in a retrospective longitudinal study with a median observation time of 11 months. A combined method assessment (CMA), defining “positive” a sample if at least one method gave “positive” results, was also tested. Eleven out of 55 screening samples and 53 out of 166 follow-up samples resulted positive at clinical evaluation. FCM and CM were concordant with positive clinical assessment in 68.5% and 51.5% of cases, respectively. According to CMA, 10.5% of samples (resulting false negative by either FCM or cytomorphology) were rescued as true positive. FCM retained significantly higher accuracy than cytomorphology (p = 0.0065) and 100% sensitivity when at least 220 leukocytes were acquired. CMA accuracy was higher than FCM accuracy and significantly higher than cytomorphology accuracy in the analysis of all samples (p < 0.0001), samples from mature B/T cell neoplasms (p = 0.0021), and samples drawn after intrathecal treatment (p = 0.0001). When acquiring ≤220 leukocytes, FCM accuracy was poor, and combining cytomorphology added statistically significant diagnostic advantage (p = 0.0043). Although FCM is the best diagnostic tool for evaluating CSF, morphology seems helpful especially when clinically positive follow-up samples are nearly acellular.