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Our purpose was to empirically validate the official New Zealand (NZ) serious non-fatal ’all injury' indicator. To that end, we aimed to investigate the assumption that cases selected by the indicator have a high probability of admission. Using NZ hospital in-patient records, we identified serious injury diagnoses, captured by the indicator, if their diagnosis-specific survival probability was ≤0.941 based on at least 100 admissions. Corresponding diagnosis-specific admission probabilities from regions in Canada, Denmark and Greece were estimated. Aggregate admission probabilities across those injury diagnoses were calculated and inference made to New Zealand. The admission probabilities were 0.82, 0.89 and 0.90 for the regions of Canada, Denmark and Greece, respectively. This work provides evidence that the threshold set for the official New Zealand serious non-fatal injury indicator for ’all injury' captures injuries with high aggregate admission probability. If so, it is valid for monitoring the incidence of serious injuries.

ObjectiveTo examine whether supplementary interview participation was comparable for occupationally injured patients attending two hospital emergency departments and to investigate the magnitude of selection bias in relation to sex, age, severity, job tasks and industry risk level.MethodsWorkers aged 18–70 years who contacted the two emergency departments for an acute occupational injury in 2013 were eligible and given a short questionnaire. Following written consent, a semi-structured interview concerning health and transient risk factors was conducted by telephone. The two departments were compared for study recruitment by age and sex. Respondents and non-respondents to the interview were compared for age, sex, injury severity, job tasks and industry risk level.ResultsOf 4002 patients attending the two hospitals, 1693 (42%) participated in the interview. One hospital had a markedly higher response rate to the questionnaire, but the proportions of participation in the interview were similar in the two hospitals. Patients aged <30 years were over-represented among non-respondents whereas sex, injury severity, job task and industry risk level were not significantly different between respondents and non-respondents.ConclusionsDespite a relatively low interview participation rate among injured individuals attending the emergency department, selection bias was limited. This indicates that results regarding injury risk patterns may be more widely generalisable when examining the causality of occupational injuries. However, the study also showed that young injured workers were less likely to participate in follow-up interviews, which is an important factor when interpreting age-related risk of injury.