Seasonality, age, gender and general clinical and laboratory profile of Cases and Controls.

<p>Seasonality, age, gender and general clinical and laboratory profile of Cases and Controls.</p

Pattern of infections in children with undifferentiated fever.

<p>Pattern of infections in children with undifferentiated fever.</p

Pattern of illnesses in febrile children with differentiated fever.

<p>Pattern of illnesses in febrile children with differentiated fever.</p

Presenting features in children with LVD versus children with other infections.

<p>Presenting features in children with LVD versus children with other infections.</p

Association between the prevalence of LVD and age, gender, season, and clinical status on presentation.

<p>Association between the prevalence of LVD and age, gender, season, and clinical status on presentation.</p

Prevalence of undifferentiated fever and contribution of LVD and malaria parasitaemia to undifferentiated fever in Cases with febrile versus non-febrile convulsions.

<p>Prevalence of undifferentiated fever and contribution of LVD and malaria parasitaemia to undifferentiated fever in Cases with febrile versus non-febrile convulsions.</p

Development and evaluation of antibody-capture immunoassays for detection of Lassa virus nucleoprotein-specific immunoglobulin M and G

<div><p>Background</p><p>The classical method for detection of Lassa virus-specific antibodies is the immunofluorescence assay (IFA) using virus-infected cells as antigen. However, IFA requires laboratories of biosafety level 4 for assay production and an experienced investigator to interpret the fluorescence signals. Therefore, we aimed to establish and evaluate enzyme-linked immunosorbent assays (ELISA) using recombinant Lassa virus nucleoprotein (NP) as antigen.</p><p>Methodology/Principal findings</p><p>The IgM ELISA is based on capturing IgM antibodies using anti-IgM, and the IgG ELISA is based on capturing IgG antibody–antigen complexes using rheumatoid factor or Fc gamma receptor CD32a. Analytical and clinical evaluation was performed with 880 sera from Lassa fever endemic (Nigeria) and non-endemic (Ghana and Germany) areas. Using the IFA as reference method, we observed 91.5–94.3% analytical accuracy of the ELISAs in detecting Lassa virus-specific antibodies. Evaluation of the ELISAs for diagnosis of Lassa fever on admission to hospital in an endemic area revealed a clinical sensitivity for the stand-alone IgM ELISA of 31% (95% CI 25–37) and for combined IgM/IgG detection of 26% (95% CI 21–32) compared to RT-PCR. The specificity of IgM and IgG ELISA was estimated at 96% (95% CI 93–98) and 100% (95% CI 99–100), respectively, in non-Lassa fever patients from non-endemic areas. In patients who seroconverted during follow-up, Lassa virus-specific IgM and IgG developed simultaneously rather than sequentially. Consistent with this finding, isolated IgM reactivity, i.e. IgM in the absence of IgG, had no diagnostic value.</p><p>Conclusions/Significance</p><p>The ELISAs are not equivalent to RT-PCR for early diagnosis of Lassa fever; however, they are of value in diagnosing patients at later stage. The IgG ELISA may be useful for epidemiological studies and clinical trials due its high specificity, and the higher throughput rate and easier operation compared to IFA.</p></div

Analytical performance of IgM and IgG ELISA in detecting Lassa virus-specific antibodies in 576 serum samples from a Lassa fever endemic area in Nigeria using IFA as a reference method.

<p>Analytical performance of IgM and IgG ELISA in detecting Lassa virus-specific antibodies in 576 serum samples from a Lassa fever endemic area in Nigeria using IFA as a reference method.</p

Comparison of RF- and CD32-based IgG ELISA results obtained from 776 sera.

<p>The S/CO values obtained with the RF ELISA were plotted against the S/CO values of the CD32 ELISA. The cut-offs for both assays are indicated by horizontal and vertical dotted lines. The number of samples per quadrant is also given. The regression curve is shown as straight line. Samples from Lassa fever non-endemic and endemic countries were plotted separately.</p

IgM and IgG ELISA results in patients grom various settings.

<p>IgM and IgG ELISA results in patients grom various settings.</p