Validity of patient stratification models based on prognostic burn index

More than 30% of patients with skin burns have inhalation injury (InI). InI worsens clinical status and increases the risk of death. Not all prognostic burn indexes include InI or do not adequately assess severity. Validity of patient stratification models based on prognostic indices was not studied in samples simultaneously consisting of patients with and without InI. Objective. To assess validity of patient stratification models based on prognostic burn indexes in relation to mixed patient samples. Material and methods. The study included 399 patients with skin burns. Of these, there were 140 (35%) ones with InI. There were 283 (71%) men. Age of patients was 50 (36; 66) years, total burn area — 25% (15; 40) of body surface area (BSA), superficial burn area — 20% (10; 30) of BSA, deep burn area — 8% (3; 20) of BSA. RFI (Revised Frank Index), FI (Frank Index), Baux, ABSI scores for predicting the outcome of burn injury were calculated for all patients. They were stratified into groups depending on scores and cause of injury. Mortality in patients with and without InI analyzed using pairwise selection. Validity of indices was assessed by the number of deaths among patients with and without InI in each stratification group. Results. The risk of mortality is 2.2 times higher in patients with burns and InI compared to patients without InI (OR 2.2, 95%CI 1.1—4.5, p=0.036). When comparing mortality among patients with burns and burns with InI in RFI-adjusted groups, we found no differences. This indicated validity of RFI-based model for stratifying patients with different etiological factors. When assessing stratification models based on other indices, it turned out that the groups of patients with burns and burns with InI were significantly different in the number of deaths: FI — in the group of 31—60 points, Baux — 81—100 and ≥101 points, ABSI — 10—11 and ≥12 points. Conclusion. The risk of mortality is 2.2 times higher in patients with burns and InI compared to patients without InI. The RFI-based model is valid for stratifying burn injury patients by probability of death.