Evaluation of Pastorex meningitis kit performance for the rapid identification of Neisseria meningitidis serogroup C in Nigeria

Background: Neisseria meningitidis serogroup C (NmC) has caused outbreaks in Nigeria of increasing size in three consecutive years since 2013. Rapid diagnostic tests (RDTs) for meningitis can facilitate quick identification of the causative pathogen; Pastorex can detect N. meningitidis serogroups A, C (NmC), Y/W135, N. meningitidis serogroup B/Escherichia coli K1, Haemophilus influenzae type b (Hib), Streptococcus pneumoniae, and group B Streptococcus. There is no published field evaluation of Pastorex in the identification of NmC. We report our experience with Pastorex in detecting NmC in field conditions. Methods: During sequential outbreaks of NmC in Nigeria in 2013, 2014 and 2015, cerebrospinal fluid (CSF) was collected from suspected cases of meningitis that met the case definition. Pastorex latex agglutination rapid test was done in the field and trans-isolate media were inoculated with CSF for culture and/or PCR, which was used as the reference standard for 63 paired samples. Results: The sensitivity of Pastorex for NmC was 80.0% (95% CI 65.4-90.4%) and the specificity was 94.4% (95% CI 72.7-99.9%). The positive likelihood ratio (LR) was 14.4 (95% CI 2.1-97.3) and negative LR was 0.2 (95% CI 0.1-0.4). The positive and negative predictive values (PPV and NPV) were 97.3% (95% CI 85.8-99.9) and 65.4% (95% CI 44.3-82.8), respectively, with a prevalence estimate of 71.4% (95% CI 58.6-82.1). Conclusion: Pastorex showed good performance in detecting NmC under field conditions. Prepositioning Pastorex at peripheral health facilities during non-epidemic periods is constrained by a short shelf-life of 1 month after the kit is opened. There is need for development of RDTs that are cheaper and with less challenging requirements for storage and usage.