Dilemma in Diagnosis of Pyogenic Meningitis in Cerebrospinal Fluid Contaminated with Blood: Does Leucocyte Esterase Test Help?

Context: Pyogenic meningitis is often a devastating condition which is diagnosed by analysis of cerebrospinal fluid (CSF) obtained by lumbar puncture (LP). CSF thus obtained can get contaminated with peripheral blood leucocytes during LP which renders it unusable for cytological analysis. Leucocyte esterase strips are available for identifying leucocyte esterase activity in urine and other body fluids which suggest inflammation. We conducted this experiment to see whether the leucocyte esterase strip can differentiate between neutrophils invited at the inflammatory site and circulating neutrophils in CSF.

Aim: To compare the diagnostic ability of the leucocyte esterase test between pyogenic meningitis and CSF contaminated with circulating neutrophils.

Setting and Design: Prospective analytical study conducted in a tertiary care hospital.

Materials and Methods: The CSF samples of pyogenic meningitis patients were analyzed for leucocyte esterase activity. The other group was normal CSF which was deliberately contaminated with buffy coat preparation, and leukocyte esterase activity was determined.

Statistical Analysis: Diagnostic ability of a test in terms of sensitivity and specificity.

Results: Overall sensitivity of the dipsticks in diagnosing pyogenic meningitis is 81% and specificity is 99%. When compared with experimentally contaminated CSF sample, a reading of 2+ on the strip had a sensitivity of 70% and specificity of 100% for pyogenic meningitis.

Conclusion: Leucocyte esterase strip is specific for pyogenic meningitis (activated neutrophils), and hence can differentiate from CSF contaminated with blood.