Figure 1 - Linearity of HEV IgG determination over multiple
dilution levels. Three samples in which HEV IgG was detectable at high
levels were serially diluted in HEV IgG negative serum and measured in
duplicate. The 1:64 dilution proved negative in both the recomWell HEV
IgG assay (cut-off 20 U/ml) (a) and the LIAISON® Murex anti-HEV IgG
assay (cut-off 0.3 IU/ml) (b). The 1:16 dilution level was consistently
found to be positive in the recomLine HEV IgG assay, while at the 1:32
dilution level only one of the three sera was positive in the
immunoblot. The raw data can be found in the supplement.
HEV-IgM
The recom Well HEV IgM and the LIAISON® Murex anti-HEV IgM
immunoassays were compared by analyzing 102 serum samples. A sensitivity
of 67.9 % [95% CI, 0.54 to 0.79] and a specificity of 100%
[95% CI, 0.91 to 1.00] was calculated (Table 2). An aberrant result
was demonstrated in 17 samples, so the WANTAI HEV IgM immunoassay was
used to decide how to score these sera. Nine out of 17 samples were
quoted HEV IgM negative by the WANTAI assay and confirmed the result of
the LIAISON® Murex IgM CLIA (Supplementary data). Thus, a sensitivity of
81.8% [95%CI, 0.68 to 0.91] and a specificity of 100% [95% CI,
0.91 to 1.00] was calculated for the LIAISON test. When immunoblot
results were considered, the sensitivity and specificity of the latter
was 88.9 % [95% CI, 0.71 to 0.97] and 53.9 % [95% CI, 0.35 to
0.71], respectively (Table 2). HEV RNA was not detected in any of the
17 discrepant sera by RT-PCR.
Table 2 – Agreement of the recomWell/recomLine HEV IgM and
DiaSorin LIAISON® Murex anti-HEV IgM immunoassays. The raw data can be
found in the supplement.* HEV RNA was not detected in these 17 samples
by RT-PCR. In the recomWell HEV IgM test, a borderline result means that
the antibody concentration is in the range of 20 to 24 IU/ml.