Indian Pediatrics 1999;36: 955-956
Evaluation of Leukocyte Esterase Reagent Strips for Rapid Diagnosis of Pyogenic Meningitis
The urine dipstick leukocyte esterase test uses the ability of esterase enzyme present in the polymorphonuclear leucocytes to convert a cetates to phenols. The resultant alcohol is detected by a color change in an indicator. The urine dipstics that detects leukocyte esterase are not available at present at India. However, the chemistry involved in the test is quite simple. We conducted this study using imported urine dipsticks to see if the test could be used reliably to detect CSF polymorphonuclear leukocytes in India, as a prelude to developing an indigenous leukocyte esterase test. Thirty six patients with clinical suspicion of pyogenic meninigitis had lumbar puncture performed on them. The CSF was cultured and tested for cells, protein and glucose by standard laboratory techniques. The CSF was also tested by the Bayer Multistix (Bayer Diagnostics, Bayer plc, Evans House, Hamilton Close, Basingstoke Hampshire RG21 2YE UK). Laboratory values of CSF glucose, protein and leukocytes and cultures were used to arrive at the diagnosis of meningitis using the criteria utilized by Moosa et al.(1). The dispstick leukocyte was tested against microscopic evidence of leukocytes and also against the diagnosis of meningitis reached using the above criteria.
Fourteen of the 36 cases were confirmed to have meningitis by laboratory criteria. All 14 of them had microscopic evidence of CSF polymorphonuclear leukocytosis. Of these, 12 were picked up by dipstick. Five samples tested positive by dipstick although their microscopic results were negative. Thus dipstick had a sensitivity of 85.26% and specificity of 77.27% in detecting pyogenic meningitis. Protein was raised above 45 mg/dl in 20 of the 36 patients. All but one of those with menin-gitis had a rise in protein. The one patient with meningitis but low protein had CSF pleocytosis detected by dipstick.
Our results are comparable to that of Molyneux and Walsh(2) who also used the Bayers urine dipstick to detect CSF polymorphonuclear leukocytes. They found a sensiti-vity of 66% for diagnosis of pyogenic meningitis. The sensitivity was 100% for cloudy CSF and 33% for clear CSF.
Two cases of meningitis in our sample would have been missed if the leukocyte esterase test was used alone to make the diagnosis. This is an unacceptably high number. In their original study, Moosa et al.(1) found that using the additional dipstick tests for protein (>50 mg/dl) and sugar (<2.8 mmol/1) alongside the leukocyte esterase test, as available in the Combur reagent strip, the pickup rate was 100%.
The addition of a test for protein like the Pandy test(3) which is a saturated solution of phenol and which becomes turbid on addition of CSF with protein >40 mg/dl may improve the pick up rate of meningitis. In our study, one patient with pyogenic meningitis had protein less than 40 mg/dl, but had CSF polymorphonuclear leukocytosis which was picked up by leukocyte esterase test.
In conclusion, our study shows that results comparable to western literature can be achieved in India by using the leukocyte esterase test to detect CSF pleocytosis. An indigenously developed leukocyte esterase test, especially if used along with the Pandy test, may have a role in the diagnosis of meningitis.
1. Moosa AA. Quotum HA, Ibrahim MD, Rapid diagnosis of bacterial meningitis with reagent strips. Lancet 1995; 345: 1290-1291.
2. Molyneux E. Walsh A. Caution in the use of reagent strips to diagnose acute bacterial meningitis. Lancet 1996; 348: 1170-1171.
3. Kjeldsberg (R) Krieg AF. Pandy test: Cerebrospinal fluid and other body fluids. In: Clinical Diagnosis and Management by Laboratory Methods, 17th edn. Henry JB. Delhi. W.B. Saunders, 1st Indian Edition, All India Travellers Book Seller. 1989; pp 459-492.