The SKYNET data: demography and injury reporting in Swedish skydiving

The Swedish Parachute Association (SFF) national registry of skydiving injuries is one of the few trauma databases available for research on sport parachuting. The usefulness of this compulsory reporting system may benefit from a description of its base population and an evaluation of its sensitivity and specificity.

Cross-sectional analysis based on data collected through a web-based questionnaire (SKYNET), from all persons renewing a Swedish skydiving license 2008 (n=1049). Sensitivity was measured as the proportion of injury events fulfilling the reporting criterion (injury event requiring care of a physician) that were actually reported, by comparing the injury events reported to the SFF during the skydiving seasons 2006 and 2007 with the injury events retrospectively reported to the web-based questionnaire for the same time period. Specificity was measured as the proportion of false positives in relation to the defined reporting criterion for the same time period. Self-stated bone fractures, shoulder dislocations and cruciate ligament injuries were labeled as non-minor injuries. Factors affecting the likelihood of reporting were evaluated using logistic regression.

The response rate was 100%. The overall sensitivity of the reporting system 2006/2007 was 0.37 (95% confidence interval (CI) 0.24-0.51). With self-stated non-minor injuries as the target for reporting, the sensitivity was 0.67 (95% CI 0.43-0.85). No significant effect on reporting was found for gender, age, license level, years in the sport, total number of jumps or club affiliation. The specificity was 0.91 (95% CI 0.83-0.95). Descriptive statistics of the Swedish skydiving population show several gender differences.

The low sensitivity will yield false low incidence calculations, but as there is no evidence for differential underreporting, risk comparisons related to the candidate predictor variables appear reasonably valid. The false positive reporting warrants assortment of incoming data and a clarification of the reporting criteria. Attitudes to reporting may be of value to study, to understand the drivers and constraints for achieving a more complete notification of skydiving injuries.