Developing a systematic approach for Population-based Injury Severity Assessment (PISA): a million-person survey in rural Bangladesh

Introduction There is currently no defined method for assessing injury severity using population-based data, which limits our understanding of the burden of non-fatal injuries and community-based approaches for primary prevention of injuries. This study describes a systematic approach, Population-based Injury Severity Assessment (PISA) index, for assessing injury severity at the population level. Methods Based on the WHO International Classification of Functionality conceptual model on health and disability, eight indicators for assessing injury severity were defined. The eight indicators assessed anatomical, physiological, postinjury immobility, hospitalisation, surgical treatment, disability, duration of assisted living and days lost from work or school. Using a large population-based survey conducted in 2013 including 1.16 million individuals from seven subdistricts of rural Bangladesh, information on the eight indicators were derived for all non-fatal injury events, and these were summarised into a single injury severity index using a principal component analysis (PCA). Principal component loadings derived from the PCA were used to predict the severity (low, moderate, high) of non-fatal injuries, and were applied to the fatal injury data to assess the criterion validity of the index. The determinants of non-fatal injury severity were determined using ordered logistic regression. Results There were 119 703 non-fatal injuries and 14% were classified as high severity based on the PISA index. The PISA index accurately predicted 82% of all fatal injuries as highly severe. Non-fatal injuries of high severity were frequent with unintentional poisoning (57%) and violence (35%). Injuries of high severity were commoner among males (OR 1.16, 95% CI 1.12 to 1.21), adults 65 years and older (OR 1.30, 95% CI 1.23 to 1.36), lower socioeconomic status and intentional injuries. Education was associated with reduced odds of high severe injuries. Conclusion The PISA index provides a valid and systematic approach for assessing injury severity at the population level, and is relevant for improving the characterisation of the burden and epidemiology of injuries in non-health facility-based settings. Additional testing of the PISA index is needed to further establish its validity and reliability.