CEREBROSPINAL-FLUID CYTOLOGY IN PATIENTS WITH CANCER - MINIMIZING FALSE-NEGATIVE RESULTS

BACKGROUND. Detection of malignant cells on cytologic examination of t he cerebrospinal fluid (CSF) is the diagnostic gold standard for lepto meningeal carcinomatosis. The absence of cells is a primary endpoint f or most therapeutic trials. Unfortunately, false-negative results are common. Practical strategies are necessary to remedy this problem. MET HODS. Four physician-dependent variables (CSF sample volume, site of C SF sampling, processing time, and frequency of CSF sampling) were iden tified, and their contributions to the false-negative rate of CSF cyto logy were evaluated prospectively in 39 patients with leptomeningeal c arcinomatosis. Retrospective data were analyzed to estimate the import ance of these variables in daily practice. RESULTS. False-negative CSF cytology results correlated with small CSF volume (P < 0.001), delaye d processing (P < 0.001), not obtaining CSF from a site of symptomatic or radiographically demonstrated disease (P = 0.02), and sampling few er than two times (P < 0.001). In 1 year, 97% of CSF specimens at the study institution were of inadequate volume; >25% were processed too s lowly. CONCLUSIONS. False-negative CSF cytology results are common, bu t can be minimized by: 1) withdrawing at least 10.5 mL of CSF for cyto logic analysis; 2) processing the CSF specimen immediately; 3) obtaini ng CSF from a site of known leptomeningeal disease; and 4) repeating t his procedure once if the initial cytology is negative. (C) 1998 Ameri can Cancer Society.