The HeMoVal study protocol: a prospective international multicenter cohort study to validate cerebrospinal fluid hemoglobin as a monitoring biomarker for aneurysmal subarachnoid hemorrhage related secondary brain injury
Authors: Akeret Kevin , Buzzi Raphael M. , Saxenhofer Moritz , Bieri Kathrin , Chiavi Deborah , Thomson Bart R. , Grüttner-Durmaz Manuela , Schwendinger Nina , Humar Rok , Regli Luca , van Doormaal Tristan P. C. , Held Ulrike , Keller Emanuela , Hugelshofer Michael , Schaer Dominik J. ,   HeMoVal Research Group, Zuercher Adrian , Grob Alexandra , Abdulazim Amr , Grüter Basil , Roder Constantin , Wirz Danielle , Colombo Elisa , Schubert Gerrit A. , Hostettler Isabelle , Hägler Joshua , Etminan Nima , Helmers Muriel , Bozinov Oliver , Wang Sophie , Gentinetta Thomas , Kälin Vincens 
Published: July 2022

Abstract
Introduction
Preclinical studies provided a strong rationale for a pathophysiological link between cell-free hemoglobin in the cerebrospinal fluid (CSF-Hb) and secondary brain injury after subarachnoid hemorrhage (SAH-SBI). In a single-center prospective observational clinical study, external ventricular drain (EVD) based CSF-Hb proved to be a promising biomarker to monitor for SAH-SBI. The primary objective of the HeMoVal study is to prospectively validate the association between EVD based CSF-Hb and SAH-SBI during the first 14 days post-SAH. Secondary objectives include the assessment of the discrimination ability of EVD based CSF-Hb for SAH-SBI and the definition of a clinically relevant range of EVD based CSF-Hb toxicity. In addition, lumbar drain (LD) based CSF-Hb will be assessed for its association with and discrimination ability for SAH-SBI.

Methods
HeMoVal is a prospective international multicenter observational cohort study. Adult patients admitted with aneurysmal subarachnoid hemorrhage (aSAH) are eligible. While all patients with aSAH are included, we target a sample size of 250 patients with EVD within the first 14 day after aSAH. Epidemiologic and disease-specific baseline measures are assessed at the time of study inclusion. In patients with EVD or LD, each day during the first 14 days post-SAH, 2 ml of CSF will be sampled in the morning, followed by assessment of the patients for SAH-SBI, co-interventions, and complications in the afternoon. After 3 months, a clinical follow-up will be performed. For statistical analysis, the cohort will be stratified into an EVD, LD and full cohort. The primary analysis will quantify the strength of association between EVD based CSF-Hb and SAH-SBI in the EVD cohort based on a generalized additive model. Secondary analyses include the strength of association between LD based CSF-Hb and SAH-SBI in the LD cohort based on a generalized additive model, as well as the discrimination ability of CSF-Hb for SAH-SBI based on receiver operating characteristic (ROC) analyses.

Discussion
We hypothesize that this study will validate the value of CSF-Hb as a biomarker to monitor for SAH-SBI. In addition, the results of this study will provide the potential base to define an intervention threshold for future studies targeting CSF-Hb toxicity after aSAH.

Study registration
ClinicalTrials.gov Identifier NCT04998370. Date of registration: August 10, 2021.