Laboratory biomarkers of delayed cerebral ischemia after subarachnoid hemorrhage: a systematic review.

Delayed cerebral ischemia (DCI) is a severe complication of subarachnoid hemorrhage (SAH). Clinical and radiographic features of SAH may be helpful in identification of individuals prone to DCI. The aim of this systematic review was to analyze the present evidence on predictive value of blood and cerebrospinal fluid (CSF) biomarkers of DCI after SAH. We systematically searched in PubMed, Scopus, Web of Science, and Cochrane Library databases for publications before July 15, 2018, reporting correlations between blood/CSF biomarkers and occurrence of DCI and/or vasospasm in SAH patients. Included studies underwent quality assessment according to QUIPS and STARD guidelines. Level of evidence (I-IV) for each of tested biomarkers was assessed according to GRADE guidelines. Of 2181 unique records identified in four databases, 270 original articles and 5 meta-analyses were included to this review. Of 257 blood and CSF parameters analyzed in 16.914 SAH patients, there was no biomarker with positive association with DCI/vasospasm showing level I evidence. Twenty-one biomarkers achieved level II evidence and could be confirmed as predictive biomarkers. In this review, six single nucleotide polymorphisms (for EET metabolic pathways, COMT, HMGB1, ACE, PAI-1 promoter, and Hp genes) and 15 non-genetic biomarkers (pNF-H, ADAMTS13, NPY, Copeptin, HMGB1, GFAP, periostin, Tau, BNP, NT pro-BNP, hs-TnT, PA-TEGMA, MPV:PLT, NLR, and PLR) were selected as predictive DCI biomarkers. We propose that a panel analysis of the selected genetic and protein biomarker candidates would be needed for further validation in a large SAH cohort.