Statistical analysis
Categorical data were tabulated by prevalence, and Fisher’s exact test was used for comparisons. All continuous data were non-normally distributed (evaluated by histograms and QQ-plots), and comparisons were made by Mann-Whitney U-test and tabulated with median, interquartile range (IQR) with lower quartiles as 25th percentile and upper quartiles as 75th percentile and range. For mortality analysis, we followed patients from the date of tumor diagnosis until death, emigration, or the end of follow-up (October 1st, 2022). The Kaplan-Meier method was used to compare the one- and five-year survival for the children with versus without a prior musculoskeletal misdiagnosis. All statistical tests were performed under a two-sided significance level of 0.05. STATA/MP 17.0 was used for the statistical analysis.
The study was approved by the Danish Data Protection Agency (record number 1-16-02-214-16). This study followed the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) (reporting) guidelines.