A novel preservative - Revolutionizing cerebrospinal fluid cytology reporting

Cerebrospinal fluid (CSF) cytology is an important investigation in the workup of cerebrospinal diseases, with reporting recommended within two hours of collection due to risk of cellular degeneration. This is often unachievable because of issues such as delay in transportation and unavailability of trained personnel at all times in the laboratory. In addition, review, referral or ancillary investigations may be needed. The formulation of a novel CSF preservative to extend this diagnostic window period was carried out at department of Pathology, Chacha Nehru Bal Chikitsalaya, Delhi, India, between 2018-2019. The fixative comprised formaldehyde (2%), glutaraldehyde (2.5%), D+ saccharose (280 mM) and calcium chloride (1 M) in phosphate buffer (pH 7.4). Thirty CSF specimens with and without preservative were analyzed, in terms of total and differential cell counts and immunogenicity, at 0, 24 and 48 h, respectively. No significant change in cellularity, cell morphology and antigenicity was seen in the CSF with a median leucocyte count nine and 30 times higher at 24 and 48 h, respectively post-fixation (Figure A-D). A commercially available CSF fixative in comparison had a reported residual cellularity 2.3 times higher than the native CSF at 18 h post-fixation and relatively better preservation of lymphocytes. This might lead to spurious reporting in cases of mild pleocytosis and unreliable differential counts. Thus, our formulation reliably extends the diagnostic window period for CSF cytology reporting.

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Preserved morphology of (A) Lymphocytes. (B) Neutrophils after 48 h of cerebrospinal fluid (CSF) preservation. (C) Preserved antigenicity of lymphocytes for CD45 expression after 48 h of CSF. (D) Total and differential cell counts in the preserved CSF by automated cell counter.

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