Reliable Cerebrospinal Fluid Cytology and Immunocytochemistry Reporting over an Extended Period by the Addition of Aldehyde and Osmolyte-Based Preservative Solution

Abstract

Introduction: The cytological examination of cerebrospinal fluid (CSF) is an important investigation in the workup of various inflammatory, malignant, or traumatic disorders of the central nervous system. The cells in the CSF lyse and degenerate at a very fast rate owing to its low tonicity, buffering capacity, redox potential, and pH, making it crucial to examine it within 2 h of sampling. We have hereby designed an aliphatic aldehyde, osmolyte, metal halide, and a buffer-based solution which will preserve the cellular components of CSF for 48 h. Methods: Thirty-nine CSF specimens were examined within 2 h of collection, and this reading was recorded as time zero reading. The CSF specimens were then divided into two tubes with (i) pre‐servative:CSF ratio of 1:5; and (ii) no preservative. Total and differential leukocyte counts and immunocytochemistry were performed on the paired specimens at 24 h and 48 h and were compared with the readings at zero hours. Results: The preservative-containing CSF showed significantly higher cellularity than the undiluted samples at 24 h and 48 h (p < 0.001). Median cell counts observed in the preservative-containing CSF were 5 times and 12 times higher than in the undiluted CSF. Neutrophils, lymphocytes, and RBCs showed immunopositivity for MPO, CD45, and GLUT-1 at both time intervals. Conclusion: Adding the prepared preservative solution to CSF in the ratio of 1:5 can optimally preserve the CSF cells for absolute and differential quantitation, morphological assessment, and immunological testing at a later date.