Clinical application of an algorithm to screen for malignant cells in body fluids using an automated hematology analyzer

Introduction: The detection of malignant cells in body fluids (BF) with an automated hematology analyzer has been proposed as an alternative to morphological examination owing to its various advantages; however, its limitations have also been highlighted. In this study, we devised a practical algorithm to screen for malignant cells in BFs using an automated hematology analyzer. Methods: A total of 558 BF samples, including 232 cerebrospinal fluid (CSF) samples and 326 non-CSF samples, were consecutively collected. Thereafter, the results obtained using the BF mode of Sysmex XN-350 (Sysmex, Kobe, Japan) were compared with the cytological diagnosis. A cutoff was also established to screen for malignant cells using receiver operating characteristic (ROC) curve analysis based on the final clinical judgment. Results: The automated hematology analyzer showed a moderate correlation or good agreement with the existing cytological diagnosis. Further, of the ROC curves for detecting malignant cells, the absolute value of highly fluorescent cells on BF (HF-BF) in total body fluids showed the highest area under the curve (0.85 [95% confidence interval 0.82–88], p <.0001, Youden index >7×10⁶/L, sensitivity 93%, and specificity 65%). Conclusion: An automated hematology analyzer could function as a complement to cytological examination. We propose a practical and comprehensive algorithm for cytological examination that requires low- and high-resolution microscopy based on the absolute value of HF-BF in BF samples suspected of malignancy. This algorithm can more usefully detect malignant cells while taking advantage of the automated analyzer and cytological examination.