Table 1. Study characteristics.

Study	Patients included in analyses (n)	Patient characteristics	QUADAS score	Subgroups in studies and outcome definitions (if applicable)
Chai12	85	Non-selected SAH patients	6	Symptomatic vasospasm: Arterial vasospasm (DSA/CTA/TCD)+neurologic deficit Asymptomatic vasospasma: Only arterial segments demonstrating vasospasm (DSA/CTA/TCD), while patients do not have neurologicdeficit No vasospasma: no arterial vasospasm (DSA/CTA/TCD); with or without neurologic deficit due to other causes
Dankbaar6	85	Non-selected SAH patients	11	DCI: Clinical deterioration (↓ GCS of ⩾2 points lasting >2 hours or a new focal deficit), excluding rebleeding, hydrocephalus, edema, postoperative swelling, infection, and metabolic disturbance as the cause Non-DCI: Clinically stable
Hickmann14	29	Non-selected SAH patients	8	Delayed neurologic deterioration: An increase in the NIHSS score by ⩾1 point or a decrease in the GCS score ⩾1 point, which could not be accounted for by other factors such as bleeding, seizure, infection, edema, electrolyte- or acid-base disturbances No delayed neurologic deterioration
Kanazawa15	19	Non-selected SAH patients	5	Symptomatic vasospasm: neurologic deficits due to vasospasm (by DSA) No symptomatic vasospasm
Killeen16	57	Non-selected SAH patients	9	DCI: New neurologic deficit distinct from baseline deficit caused by a SAH or surgical intervention, excluding rebleeding, hemorrhage, hydrocephalus, infection, metabolic disturbance, and seizure as the cause and/or a new infarction on CT/MRI after day 4 Non-DCI: Patients with none of the criteria above
Lagares7	39	Non-selected SAH patients	8	DCI: Clinical deterioration attributable to vasospasm, excluding rebleeding, hydrocephalus or electrolyte abnormalities as the cause, or a new infarct on CT related to vasospasm (not visible on admission or immediate posttreatment scan), or both Non-DCI: Patients without clinical deterioration or patients with clinical deterioration owing to other causes and without a new infarct on CT
Lanterna13	41	Non-selected SAH patients	11	DCI: A deterioration (↓ GCS of ⩾2 points or a new focal deficit), excluding rebleeding, hydrocephalus, and metabolic disturbances as the cause, with or without an infarction on the CT scan Non-DCI: Clinical deterioration owing to other causes or clinically stable
Rijsdijk10	27	Non-selected SAH patients	11	Clinical deterioration from DCI: clinical deterioration (↓ in consciousness or new focal deficit) lasting ⩾2 hours, excluding rebleeding, hydrocephalus, infections, and metabolic disturbances as the cause, with or without hypodensity on CT Non-DCI-related deteriorationb: A decrease in GCS of ⩾2 points from hydrocephalus or other medical causes (metabolic disturbances, infection) Clinically stableb
Sanelli11	96	Non-selected SAH patients	9	DCI: Clinical deterioration (↓ GCS of ⩾2 points or focal neurologic impairment), that was not apparent immediately after aneurysm occlusion and was not attributed to other causes by clinical assessment, CT or MR imaging, and laboratory studies Non-DCI: Clinical deterioration owing to other causes or clinically stable
Sviri17	46	Patients with cerebral vasospasm after aSAH	8	Delayed ischemic deterioration: worsening of neurologic condition (↓ GCS of ⩾2 points or a new hemiplegia or hemiparesis or↓muscle scale of ⩾2 points in a previously hemiparetic patient) lasting >30 minutes, excluding rebleeding, hydrocephalus, postoperative complications and systemic complications as the cause No delayed ischemic deterioration
Van der Schaaf8	46	Non-selected SAH patients	11	DCI: persisting clinical deterioration (new focal deficit and/or decrease in consciousness), excluding rebleeding, hydrocephalus, infections, and metabolic disturbances as the cause, with or without hypodensity on follow-up CT Non-DCI: clinical deterioration owing to other causes or clinically stable

aSAH, aneurysmal subarachnoid hemorrhage; CTA, CT angiography; DCI, delayed cerebral ischemia; DSA, digital subtraction angiography; GCS, Glasgow Coma Scale; MRI, magnetic resonance imaging; n, number; NIHSS, National Institutes of Health Stroke Scale; QUADAS: quality assessment of diagnostic accuracy studies;⁹ SAH, subarachnoid hemorrhage; TCD: transcranial Doppler.

^aIn the analyses, the subgroups of asymptomatic vasospasm and no vasospasm were pooled (as non-DCI).

^bIn the analyses, the subgroups of non-DCI-related deterioration and clinically stable patients were pooled (as non-DCI).