Study selection and population characteristics
The systematic search returned 289 articles, 83 of which were selected
for full text screening. Fourteen articles were considered eligible for
data extraction and meta-analysis according to our criteria of
eligibility; two articles8, 9 were parts of another of
our included articles10. The publications of Bez et
al., 2004 and Rolinck-Werninghaus et al., 2004 were found to be post hoc
analyses of the study of Kuehr et al., 2002. The study of Bez et al.,
2004 was excluded from further analyses as it did not contain any
outcome of interest, while the study of Rolinck-Werninghaus et al., 2004
was used for the outcomes of interest which were not available in the
study of Kuehr et al., 2002. Eventually, twelve studies were included in
quantitative synthesis and meta-analysis. Figure 1 shows the flow chart
of the study selection process. A summary of the characteristics of the
included studies are presented in Table 1. Briefly, 4 trials were
conducted in Europe, 4 in USA and 3 in Japan, assessing a total of 3,211
patients. Two trials included only pediatric patients, while 5 included
only adult patients (>17 years of age). In 3 trials AR was
indicated as birch/grass Seasonal Allergic Rhinitis (SAR) / Seasonal
Allergic Rhino-Conjunctivitis (SARC) in 3 trials the AR indication was
ragweed SAR and in 3 trials the AR indication was cedar SAR. In 5 trials
the symptom severity range was from moderate to severe. Omalizumab was
administered subcutaneously in all the trials every 2 or 4 weeks to
provide either a fixed dose or a dose dependent on body weight and serum
IgE levels (Table 1). The methodologic quality for the majority of
studies found to be good (Supplementary Table 1). All studies were
double blinded and almost all of them provided a sufficient description
regarding the follow-up of the patients; 5 studies performed an
intention-to-treat (ITT) analysis. Nevertheless, most of the studies did
not report adequately any methodological measurements to ensure
allocation concealment and blinding of outcome assessment.