Standardizing a volume benchmark for cerebrospinal fluids for optimal diagnostic accuracy.

INTRODUCTION

Cerebral spinal fluid (CSF) cytomorphologic analysis remains the gold standard in the evaluation of malignant leptomeningeal involvement. However, collection of optimal volumes for adequate cytomorphologic evaluation is not standardized. Our study investigated optimal CSF volumes that result in a significant diagnostic result.

METHODS

A total of 4114 samples were retrospectively identified from 2014 to 2018, and 2557 samples had concurrent flow cytometry (FC) study. Each specimen was grouped as unsatisfactory, negative, atypical, or positive. Positive samples were grouped as either solid tumors, leukemia, or lymphoma by the type of malignancy detected. Demographic data as well as CSF source was recorded. Specimens with FC were separated by detection on cytology and/or FC. A t-test and ANOVA test were used to compare the average volumes for each group.

RESULTS

Average volumes for negative, atypical, and positive samples are 7.48 mL (95% CI: 7.33, 7.63), 7.97 mL (95% CI: 7.37, 8.57), and 8.44 mL (95% CI: 7.46, 9.43), respectively. Average volumes for solid tumors, leukemia, and lymphoma positive samples are 12.0 mL (95% CI: 9.11, 14.89), 6.73 mL (95% CI: 5.94, 7.53), and 8.44 mL (95% CI: 6.78, 10.09). For cases with FC, the volumes are 10.11 mL (95% CI: 9.28, 10.96), 7.28 mL (95% CI: 6.87, 7.70), and 6.86 mL (95% CI: 6.25, 7.49) for positive cytology only, positive cytology/FC, and negative for both, respectively.

CONCLUSIONS

Our results suggest that higher volumes produce better results for analysis. We recommend an optimal volume of 8.44 mL for cytologic work-up of malignancies. However, optimal volumes may differ based upon malignancy type and utilization of flow cytometry.