The complementary use of fish extracts enhances the diagnostic
performance of the molecular approach
Besides PVs, the presence of IgE to other fish allergens should be
investigated before continuing with FC to confirm specific fish
tolerance. Our analyses showed lower IgE levels to raw and heated fish
extracts than to PVs for all bony fish (Figure 4A ). To
determine the correlation between the IgE levels for PV and RE, PV and
HE, or RE and HE, Spearman’s rank correlation coefficient was
calculated. Data were interpreted (weak/moderate/strong/very strong
correlation) according to Schober et al.17 A strong
significant positive correlation (Rho>0.7) of all three
pairs was observed for herring and salmon (Figure 4B ). In
addition, a very strong significant positive correlation (Rho=0.98)
between values for cod PV and RE was shown, indicating that for cod, a
RE is sufficient to detect the PV sensitization. For other analyzed
species, correlations of IgE levels to PVs and extracts were weak to
moderate (Figure 4B ). Data for REs and HEs correlated strongly
for herring (Rho=0.85) and salmon (Rho=0.75), while moderate to weak
correlations were observed for other species. All correlations were
significant, except for tuna PV vs RE and tuna PV vs HE (Figure
S7 ). Individual scatterplots for each species and calculated P values
for the correlation coefficients are shown in Figure S7 .
We next assembled data for patients with higher IgE values to extracts
than to PV from one or more species (44 patients in total). The
percentage of these patients varied across the countries (8% - 28%)
(Figure 4C ). Data for each patient was then analyzed in detail
(Figure 4D ). Up to 7 patients per fish species had no IgE for
the respective PV, but were positive for RE and/or HE. These patients
could be falsely diagnosed as negative to some species if only the
PV-sIgE would be quantified.