Sensitivity and specificity of clinical features and blood counts in childhood meningoencephalitis

Abstract

Meningoencephalitides (ME) are an important group of disorders that constitute a medical emergency in any age group, more so in children. The physician uses the lumbar puncture (LP) as a diagnostic test to confirm or exclude the diagnosis of ME. Of all the LPs ordered, ME is found in only a small proportion. The need for LP is often alarming to the family. The diagnostic accuracy of different clinical symptoms and signs may therefore help the physician in being more discriminative in use of LP. Setting: Pediatric wards of a teaching hospital in Northern India. Methods: Consecutive children between one month and 12 years of age undergoing LP on the suspicion of ME on three preselected weekdays were enrolled in the study and all relevant clinical features, total and differential leukocyte counts in blood were recorded. Outcome measurement was presence or absence of ME diagnosed on the basis of cerebrospinal fluid (CSF) examination for cells, protein, sugar and bacterial culture. Clinical features, total and differential leukocyte counts were compared in ME and nonME groups. Sensitivity and specificity of clinical features were computed and logistic regression and stratified analysis by age performed. Results: One hundred and nineteen patients were enrolled, of which 35 (29.4%) had ME. Only one symptom, headache, was significantly more common in ME. All the meningeal signs were more common in ME with sensitivity being highest for Vincent's sign (76.9%). Tense, bulging anterior fontanelle, focal neurological deficit, and mean polymorphonuclear (PMN) leukocyte percentage in blood were also significantly higher in ME. Logistic regression showed that only neck rigidity and PMN leukocyte percentage were significant independent predictors of ME. In children beyond 24 months of age, fever was present in 19 out of 20 cases of ME. Presence of fever and headache achieved high sensitivity while neck rigidity, Vincent's sign and focal deficits had high specificity in this age group. In children below 12 months of age, none of the signs achieved adequate accuracy. Conclusions: In hospitalized children undergoing LP on suspicion of ME, neck stiffness along with high PMN leukocyte percent (> 80%) in peripheral blood are highly suggestive of ME. Absence of fever beyond two years of age almost rules out ME. However, no clinical features are adequately discriminative for the diagnosis of ME in infants.