Background Quality indicators have become increasingly important in the healthcare sector. Data from a trauma registry (TR) should be accurate and reliable as they are used to describe and evaluate (the quality of) trauma care.

Objective To investigate the reliability of injury coding, injury severity scoring and survival status in a regional TR. The feasibility of the format that was developed for this study was also investigated.

Methods A random sample, without replacement, was taken from the TR of a Dutch regional trauma care network. All 343 patients in the sample were then recoded by another trauma registrar (rater). Reliability was expressed in the percentage agreement between the raters.

Results In the total study sample of 333 patients, the reliability of the number of Abbreviated Injury Scale (AIS) codes was substantial (intraclass correlation coefficient (ICC)=0.70); and the reliability of the Injury Severity Score (ISS) (ICC=0.84) and survival status were ‘almost perfect’ (Cohen's κ=0.82). Both raters had given 129 patients one AIS code. The reliability of the body region of the AIS was ‘almost perfect’ (Cohen's κ=0.91); and the reliability of the severity of the injury and the ISS were ‘almost perfect’ (weighted κ=0.88 and ICC=0.90). The reliability of the ISS in the patients who were assigned at least two AIS codes (n=128) was ‘almost perfect’ (ICC=0.86). The reliability of the number of AIS codes and the number of body regions was ‘moderate’ (ICC=0.56 and Cohen's κ=0.52).

Conclusions The reliability of injury coding in a regional trauma registry was ‘substantial’ and the reliability of the ISS and survival status was ‘almost perfect’. The format and design of this study were feasible and could be used to investigate the quality of (trauma) registries.