Largely a clinical diagnosis, based on history and clinical examination.
Guillain-BarréDisability Scale (Hughes disability score) can help stratify risk.
Lung function tests – Forced Vital Capacity can quantify any deterioration and help inform decisions on critical care referral and requirement for intubation.
CSF – may show elevated protein count, typically after 5-7 days of disease, or may point to alternative diagnosis.
Blood tests – raised IgG, antiganglioside GM1 antibody, GQ1b antibody in Miller Fisher variant.
