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Additional information (online repository)
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Supplementary analyses
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Methods
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In order to evaluate further the usefulness of baseline clinical and immunological parameters
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to predict the severity, frequency and persistence over time of OIT-related reactions, we
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performed the following analyses:
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1. First, we studied parameters associated to experiencing grade 4 dose-related
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reactions using comparative analysis between groups, followed by multivariate logistic
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regression.
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2. Secondly, we assessed the correlation between reactions frequency (percentage of
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OIT-doses that associated reaction in each individual) and baseline parameters using the
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Spearman correlation coefficient.
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3. Finally, we analysed safety from a survival analysis perspective, focusing on the time
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needed for each patient to stop reacting to egg-OIT doses, i.e. to resolve dose-related
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reactions whilst on-OIT. The cumulative probability of reactions resolution over time was
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determined using Kaplan-Meier estimator, i.e. this estimator indicates the percentage of
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children who have stopped reacting to egg-OIT doses at each time interval whilst on-OIT (or
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inversely, the percentage of children who still suffer from dose-related reactions at each time
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interval). Baseline risk factors for requiring longer time to stop reacting whilst on-OIT were
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studied by stratified Kaplan-Meier analysis as well as by multivariate proportional hazards Cox
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regression model. The event of interest for survival analysis was defined as “reactions
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resolution”, i.e. absence of further reactions during the whole period on-OIT since the last
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reaction registered. Accordingly, children were classified on the final evaluation into two
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categories to perform the survival analysis, as explained in the main manuscript: subgroups PR
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(children with ongoing dose-related reactions over the whole period on-OIT) and RR (children
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who stopped reacting to egg-OIT doses over time, being free of reactions for at least for the
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last 4 months on-OIT). The time point when the last dose-related reaction had occurred was
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registered as the moment when a given child of subgroup RR had stopped reacting to OIT-
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doses. Children who discontinued OIT in maintenance phase due to ongoing reactions were
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included in the survival analysis as subgroup PR. In contrast, children in subgroup ED were
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classified separately and excluded from survival analysis due to their shorter time on egg-OIT.
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Results
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1. Factors associated to reactions severity
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Children who experienced grade 4 OIT-related reactions (n=29), compared to children
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who did not (n=21), had a higher rate of grade 4 reactions at DBPCFC (36.7% vs. 9.5%,
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p=0.048), more severe forms of asthma (p=0.033), as well as higher EW-sIgE and OVM-sIgE
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(10.95 and 8.59 kU/L vs. 3.43 and 2.28, p=0.047 and 0.021, respectively). No other differences
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were found in clinical/immunological parameters between these two groups (data not shown).
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Parameters found significant in univariate analysis were included in the multivariate logistic
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regression model, which revealed that having a grade 4 reaction at DBPCFC was the only
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independent predictor for experiencing grade 4 reactions during OIT (Odds ratio: 7.08 (CI 95%:
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1.31-38.19), p=0.023).
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2. Factors associated to reactions frequency
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A moderate correlation was found between sIgE to EW, OVA and OVM and
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reactions/doses per child (Rho Spearman: 0.559, 0.509 and 0.594, respectively, p<0.001). The
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severity of reaction at DBPCFC showed also a low but significant correlation (0.391, p=0.005).
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SPT and threshold dose at DBPCFC showed no correlation with reactions frequency (p>0.05).
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3. Factors associated to reactions persistence
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The cumulative probability of reactions resolution -i.e. the percentage of children who
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had already stopped reacting to OIT-doses- was 25% after 6 months on OIT (95% CI: 3-9) and
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50% after 13 months (95% CI: 7.3–18.8) (Fig.E1 in online repository).
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Two parameters were identified as independent risk factors for requiring longer to
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stop reacting to OIT-doses over time: EW-sIgE and grade 3-4 reaction at baseline DBPCFC
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(hazard ratios: 1.16 for increases in 1 kU/L (95% CI: 1.05-1.27, p=0.002) and 4.4 (95% CI: 1.78–
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10.87, p=0.01) respectively). Indeed, the severity of reaction at DBPCFC influenced the time
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required to stop reacting to OIT-doses as follows: for severity grades 1-2 the cumulative
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probability of reactions resolution was 50% at 6 months (CI 95%: 0-12.5), whereas for grades 3-
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4 it was 50% at 16 months (CI 95%: 11.5-20.5, p=0.003) (Fig. E2 in the online repository). The
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time needed to stop reacting was not influenced by other clinical/immunological parameters
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(data not shown).
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Table E1. Univariate logistic regression analysis, showing baseline risk factors for belonging
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to subgroup RR (children who stop reacting to egg-OIT doses over time) as opposed to
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subgroups PR (children with ongoing reactions over the whole period on-OIT) and ED
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(children requiring early OIT discontinuation due to frequent reactions not improved by
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medication or protocol re-adaptation). 1Those children who experience a grade 1-2 reaction
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at baseline DBPCFC [20] have 4.65-times increased probability of belonging to subgroup RR in
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comparison to those who experience a grade 3-4 reaction. 2The higher the baseline IgE levels,
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the lower the probability of belonging to subgroup RR. 3Each increase in OVM-sIgE in 1 kU/L
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involves 0.81-times reduced probability of belonging to subgroup RR. Inversely, each increase
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in OVM-sIgE in 1 kU/L involves 1.23-times (1/0.81=1.23) increased probability of belonging to
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subgroups PR or ED, whereas an increase in 10 kU/L involves 8.2-times (1.2310=8.2) increased
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probability of belonging to PR or ED.
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Univariate logistic regression
Baseline parameter
Reaction severity at DBPCFC
(grades 1-2 vs 3-4)
EW-sIgE (KU/L)
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OVA-sIgE (KU/L)
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OVM-sIgE (KU/L)2,3
Total IgE (kU/L)
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Odds ratio
95% CI
P value
4.65
1.23-17.1
0.024
0.79
0.67-0.92
0.003
0.69
0.54-0.88
0.003
0.81
0.69-0.94
0.005
0.99
0.98-0.99
0.044
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Figures legends for online repository
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Figure E1. Kaplan–Meier estimate of survival, which represents the percentage of children
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who still suffer from dose-related reactions at each time interval whilst on oral
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immunotherapy (OIT).
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The event of interest is defined as “resolution of dose-related reactions”, i.e. absence of
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further reactions over the whole period on-OIT since the last reaction registered. (n =41,
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children in subgroup ED (who required discontinuation in induction phase due to frequent
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reactions not improved by medication and protocol re-adaptation) were excluded due to their
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shorter period on-OIT).
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Figure E2. Kaplan–Meier estimate of survival, showing the percentage of children who still
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suffer from dose-related reactions at each time interval whilst on-OIT, stratified by reactions
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severity at baseline double-blind placebo-controlled food challenge (DBPCFC) [21]. The event
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of interest is defined as “resolution of dose-related reactions”, i.e. absence of further reactions
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over the whole period on oral immunotherapy (OIT) since the last reaction registered. (n =41,
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children in subgroup ED (who required discontinuation in induction phase due to frequent
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reactions not improved by medication and protocol re-adaptation) were excluded due to their
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shorter period on-OIT).
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