Guillian-Barré syndrome: Epidemiology and biomarkers in blood and cerebrospinal fluid

Abstract

Guillain-Barré syndrome (GBS) is a rare, potentially life-threatening disease. The incidence of GBS varies, and clusters can occur related to the increased prevalence of triggering events. Most patients recover well, but some are left with permanent disability or die. This thesis aimed to investigate the epidemiological aspects of Guillain-Barré syndrome in Iceland and the Västra Götaland region (VGR) and explore potential fluid biomarkers for diagnosis and outcome. Papers I and II are retrospective population-based epidemiological studies. Paper I studies the incidence and long-term outcomes of GBS in Iceland from 1995 to 2014. The average annual incidence was 1.1 per 100.000 person-years. At the last follow-up, an average of 6.5 years, 14% had severe disability. Mortality was increased up to three years after diagnosis. Paper II investigated the impact of the COVID-19 pandemic on the incidence of GBS in the VGR. The incidence significantly decreased during the pandemic compared to the years immediately prior. Papers III and IV are retrospective cohort studies on fluid biomarkers in GBS. In paper III, neurofilament light chain (NfL) parameters were explored as diagnostic and prognostic markers in GBS. The results show that serum NfL Z-score at diagnosis predicts short- and long-term outcomes. Patients with GBS had lower NfL CSF/serum ratio and NfL index (NfL ratio/albumin quotient) than healthy controls, patients with multiple sclerosis and amyotrophic lateral sclerosis. In paper IV, brain-derived tau (BD tau) was investigated as a prognostic biomarker in GBS, and high levels at diagnosis were associated with poor outcomes after one year. The incidence of GBS varies over time but is, on average, similar in similar demographics. The decreased prevalence of triggering infections due to social restrictions led to a decrease in the incidence of GBS during the COVID-19 pandemic. The serum NfL Z-score is a promising biomarker for prognosis, while the NfL ratio and the NfL index have potential as diagnostic biomarkers. BD-tau is a potential biomarker for long-term outcomes, which indicates that the degree of CNS involvement is crucial for long-term recovery.