Cerebrospinal fluid appearance as a diagnostic criterion for suspected bacterial meningitis in children less than five years in East Africa.

Abstract

The study focused on the sensitivity and specificity of cerebrospinal fluid appearance and white blood cell (WBC) count as potential laboratory screening indicators compared to culture method. This is because Cerebrospinal fluid (CSF) culture facilities are expensive and difficult to maintain in resource poor laboratory settings yet this is the gold standard for diagnosis. Early signs of meningitis are often subtle and nonspecific resulting in unacceptably high mortality and morbidity rates in children, especially those from developing countries where rapid access to medical attention and resources is unavailable. Diagnosing acute bacterial meningitis in children is likely to be missed in a third of cases at district hospitals in sub-Saharan Africa where adequate and reliable laboratory resources are lacking. Most affected patients now survive due to antibiotic use, though many children still die or suffer permanent neurologic sequelae as a result of bacterial meningitis. Data was gathered from samples collected from children aged below five years admitted at the participating hospitals between the time periods 2001 to 2008. This was carried out retrospectively from the period 2001 to 2005 and prospectively from 2006 to 2008. A total of 32,152 samples were collected for the entire period. Of the 29,153 samples collected with reported appearance, 4.49% of them were positive for pathogenic organisms out of which three micro-organisms were of most interest to the surveillance; Streptococcus pneumoniae, Haemophilus influenzae and Neisseria meningitidis that accounted for 50.7% of the positive isolates. Turbid appearance had a sensitivity of 72% (95% CI 69 – 74) and specificity of 96%. Clear appearance had a sensitivity of 18% (95% CI 16.1 – 20.3) and a specificity of 17%. White blood cell count greater than 5 (WBC>5) per microlitre had a sensitivity of 81.5% (95% CI 77.2 - 85.3) and a specificity of 78.7%. White blood cell count greater than 10 (WBC>10) per microlitre had sensitivity of 80.1% (95% CI 75.7 – 84) and specificity of 91.3%. The 32,152 samples were also divided into Pre- and Post- Hib eras to account for the introduction of the Haemophilus influenzae type b vaccine that was introduced in the region. The pre-Hib, vaccine era accounted for 26.8% of the samples of which 5.0% were culture positive. The post-Hib data accounted for 73.2% of the total samples of which, 11.8% were culture positive. Although the number of positive isolates in the pre and post Hib eras varied significantly, there were insignificant differences in the sensitivities and specificities of turbidity and white cell counts. The recommendation is that, presence of a turbid sample is a good indicator of presence of an etiological agent. However, using (one evaluation method) appearance alone is not adequate. Additional use of white blood cell counts, as a screening criterion should be included to increase the test sensitivity to a point where it is useful for surveillance. The benefit of this study results is that this information can be used to advise laboratory personnel on what minimum criteria can be used to analyze CSF samples to reduce on missed cases and also maximize on the limited laboratory resources.