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To the Editor.—
Mazor et al1 have attempted to clarify an age-old dilemma concerning traumatic lumbar punctures. The use of the white blood cells (WBC)/red blood cells ratio and the observed/predicted ratio seem to be helpful in determining who doesn’t have a positive cerebrospinal fluid (CSF) culture. Unfortunately, the authors fail to point out an underlying confound in the literature and in their data. Patients with a positive culture from blood CSF may not necessarily have meningitis but rather may have bacteremia. I see no easy way to determine in those cases where the WBC count is not clearly markedly different from the peripheral WBC count (and the glucose and protein aren’t equally different) that the positive CSF culture doesn’t reflect bacteria introduced from the peripheral blood. It would be reassuring to know whether the peripheral blood culture was negative (assuming an adequate sample was drawn) before determining whether a positive CSF culture represented meningitis, but even this is not foolproof. The final word is not in yet!
REFERENCE
In Reply.—
In their informative article about traumatic lumbar punctures, Mazor et al1 report results from 57 patients with blood-stained cerebrospinal fluid (CSF) samples with an emphasis on predicting patients without meningitis. In sub-Saharan Africa there are up to 500 000 childhood deaths each year from bacterial meningitis.2 The clinical features of meningitis overlap with those of malaria, a common cause of admission to hospital. Most health facilities do not have the capability to culture CSF for bacterial pathogens. Thus, the accuracy and correct interpretation of simple microscopy and testing of CSF are vitally important. We conducted a prospective study of invasive bacterial infections in children at a rural Kenyan district hospital. Our lumbar-puncture policy is designed to include all children admitted to the hospital with a possibility of bacterial meningitis and has been described elsewhere.3 CSF cell counting was done manually by using a modified Neubauer counting chamber at x400 magnification.
From August 1998 through July 2002, 515 of 3668 (14%) lumbar punctures performed in children >1 month old yielded a blood-stained CSF (erythrocytes 
500 cells/µl). In 324 (63%) of these, a leukocyte count was possible, and in 191 (37%) the CSF was too bloody to count the cells. Children with uncountable CSF leukocytes were younger than the others (see Table 1). Mazor et al did not give results for the simple CSF leukocyte count. We found it to be as predictive of culture-proven meningitis as either of the other ratios described in blood-stained CSF samples. We also found that another simple test, the CSF/blood glucose ratio was highly effective in predicting culture-proven bacterial meningitis irrespective of blood staining.
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A traumatic lumbar puncture is a common event in acute pediatric practice worldwide and can lead to uncertainty about management. We have found that despite blood staining, where CSF leukocyte counting is possible, it is highly predictive of meningitis. The combination with CSF/blood glucose ratio improves sensitivity. However, 
2% of confirmed cases may still be missed with or without blood staining. Where doubt exists or the sample is too blood-stained to count leukocytes, consideration should be given to giving treatment and repeating the lumbar puncture after 24 to 48 hours.
REFERENCES
In Reply.—
We thank both Dr Holzman and Dr Berkley and colleagues for their thoughtful comments.
In our study, we were primarily interested in identifying patients without meningitis who would be appropriate for discharge despite a traumatic lumbar puncture (LP). Dr Holzman is concerned that patients with bacteremia and a traumatic LP may have a falsely positive cerebrospinal fluid (CSF) culture, overestimating the presence of meningitis. Overestimating the presence of meningitis does not interfere with our results. We considered the treatment of a few patients without meningitis acceptable, provided that no cases of meningitis were missed. Of the 12 patients with positive CSF cultures, 7 had positive blood cultures. Because meningitis and bacteremia can coexist in a patient, we do not believe the results of the peripheral blood culture will further clarify which patients had bacteremia without meningitis.
Berkley et al present their data on traumatic LPs from rural Kenya. Of 18 patients with confirmed meningitis and a traumatic LP, 1 patient had a CSF white blood cell of <10, and their meningitis would not have been predicted by the white blood cell/red blood cell or observed/predicted ratios. However, we are not presented with the value of these ratios and therefore are unable to interpret their results with regard to our conclusions. Because we were interested in predicting the absence of meningitis and believe that the treatment of a few patients without meningitis is acceptable, our conclusions still may be valid using their data. In addition, our focus was to compare the results of traumatic LPs in the post-Haemophilus influenzae vaccine era. We are not provided with the vaccine status of patients in the Kenya study.
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