The relevance of leukocytosis in patients with severe trauma: a systematic review

Abstract Background Polytrauma remains a leading cause of death in individuals younger than 40 years and poses major challenges during early resuscitation and subsequent clinical management. Beyond early mortality from hemorrhage, post-traumatic inflammatory and infectious complications such as systemic inflammatory response syndrome (SIRS), acute respiratory distress syndrome (ARDS), and multiple organ dysfunction syndrome (MODS) are of increasing clinical relevance. Leukocyte count is a simple and routinely available laboratory parameter. This systematic review aimed to evaluate whether leukocyte count on admission is associated with post-traumatic complications and mortality. Methods A systematic review in accordance with the PRISMA guidelines was conducted. PubMed/MEDLINE and EMBASE were systematically searched for original English-language clinical studies published between January 1, 2000, and July 31, 2025, that investigated leukocyte counts following adult polytrauma. After deduplication, 2,169 records were independently screened by three investigators based on titles and abstracts. Thirty-two reports were sought for retrieval, and 12 studies were finally included. Disagreements were resolved by consensus. Data on study characteristics, patient and injury characteristics, leukocyte counts and kinetics, and clinical outcomes were extracted and qualitatively synthesized. Study quality and risk of bias were assessed using the Newcastle–Ottawa Scale. A sample-size-weighted mean admission leukocyte count was calculated from the reported study-level means, and associations were analyzed using Spearman’s rank correlation. Results After subsequent screening 12 studies with overall 15,658 patients were finally included in the current review. Across all studies, leukocyte counts after trauma were elevated compared with reference values. The weighted mean leukocyte count across studies was 10.26 × 10^9/L. The proportion of blunt trauma was positively correlated with mean leukocyte count (rho = 0.775, p = 0.04). Pneumonia and SIRS were reported in three and four studies, respectively. One study reported higher mortality in patients with persistent leukocytosis after trauma. Conclusions This review demonstrates that leukocyte counts are consistently elevated following trauma. Although some studies suggested associations with morbidity and mortality, the available evidence remains insufficient for firm prognostic conclusions because of substantial heterogeneity and the predominantly retrospective design of the included studies. Further research should focus on leukocyte subpopulations, particularly neutrophils, to improve understanding of post-traumatic immune responses and their clinical relevance.