Prediction of outcome from adult bacterial meningitis in a high HIV seroprevalence, resource-poor setting using the Malawi Adult Meningitis Score (MAMS)

Background: Acute bacterial meningitis (ABM) in adults residing in resource-poor countries is associated with mortality rates in excess of 50%. To improve outcome, interventional trials and standardised clinical algorithms are urgently required. To optimise these processes we developed and validated an outcome prediction tool to identify ABM patients at greatest risk of death.

Methods: We derived a nomogram using mortality predictors derived from a logistic regression model of a discovery database of adult Malawian ABM patients (n=523, 65% CSF culture positive). We validated the nomogram internally using a bootstrapped procedure and subsequently used the nomogram scores to further interpret the effects of adjunctive dexamethasone and glycerol using clinical trial data from Malawi.

Results: ABM mortality at six week follow-up was 54%. Five of fifteen variables tested were strongly associated with poor outcome (CSF culture positivity, CSF WCC, haemoglobin, GCS and pulse rate), and were used in the derivation of the Malawi Adult Meningitis Score (MAMS) nomogram. The C- index (area under the curve) was 0.76 (95% CI 0.71 : 0.80) and calibration was good (Hosmer-Lemeshow c-statistic, =5.48, df=8, p=0.705). Harmful effects of adjunctive glycerol were observed in groups with relatively low predicted risk of poor outcome (25-50% risk): CFR 21% in the placebo group, 52% in the glycerol group p<0.001. This effect was not seen with adjunctive dexamethasone.

Conclusion: MAMS provides a novel tool for predicting prognosis and improving interpretation of ABM clinical trials by risk stratification in resource-poor settings. Whether MAMS can be applied to non-HIV endemic countries requires further evaluation.