Statistical analyses
Descriptive analysis was conducted to evaluate the pattern of PAG
problems overall and by age, year, and region. The differences in those
patterns across age, year and region were evaluated using χ2 test of
proportions. All analyses were conducted using SAS software, version 9·3
(SAS Institute Inc., Cary, NC).
The meta-analysis was conducted with Stata 16·0 (Stata Corp, College
Station, TX, USA). For each study in the systematic review, we
calculated the weighted average percentage of each article that met our
inclusion criteria by taking disease species as subgroup. Because not
all of the articles included in the meta-analysis had all disease
classifications, the disease proportion was weighted to 100% for final
analysis. By using the I2 statistic to assess
heterogeneity between studies, summarized effect size (ES) (95% CI) was
derived.