Prognostic immunonutritional indices and the clinical outcome of patients with traumatic brain injury: a systematic review and meta-analysis

Adverse immunonutritional status has been increasingly recognized as a prognostic factor in patients with traumatic brain injury (TBI). This systematic review and meta-analysis evaluated the associations between immunonutritional status—defined by a low prognostic nutritional index (PNI) or geriatric nutritional risk index (GNRI), or a high controlling nutritional status (CONUT) score—and the risks of short-term mortality and poor functional outcome after TBI. A systematic search of PubMed, Embase, Web of Science, CNKI, and Wanfang was conducted to identify longitudinal observational studies evaluating the association between prognostic immunonutritional indices and clinical outcomes in patients with TBI. Study quality was assessed using the Newcastle–Ottawa Scale (NOS). Random-effects models were applied to pool odds ratios (ORs) with 95% confidence intervals (CIs). Sensitivity analyses were performed using leave-one-out methods and by restricting to studies with adjustment for baseline Glasgow Coma Scale (GCS). Prespecified subgroup analyses were conducted according to age, baseline GCS, index type, follow-up duration, and analytic model. Twelve retrospective cohort studies involving 4,458 TBI patients were included. Six studies ( n = 1,612) evaluated mortality, among whom 437 (27.1%) died during follow-up. Adverse immunonutritional status was associated with higher odds of short-term mortality (OR: 2.69, 95% CI: 1.72–4.21; I² = 55%). The association was stronger for in-hospital mortality (OR: 4.27, 95% CI: 2.25–8.12) than for 28/30-day mortality (OR: 1.89, 95% CI: 1.11–3.21; p for subgroup difference = 0.01). Seven studies ( n = 3,211) assessed functional outcomes, with 666 (20.7%) patients experiencing poor functional outcome. Adverse immunonutritional status increased the odds of poor functional outcome (OR: 5.59, 95% CI: 3.43–9.10; I² = 64%), without significant different effects across subgroups defined by age, GCS, index type, follow-up duration, and outcome definitions. The certainty of evidence for both outcomes was rated as very low according to GRADE. These findings suggest that adverse values of commonly used prognostic immunonutritional indices may be associated with higher odds of short-term mortality and poor functional outcome in patients with TBI.