Table 1

Inclusion criteria based on the PICOD framework

PICOD	Specific details
Population	Patients who received intravenous or intra-arterial non-ionic iodinated CM* High-risk population Low-risk population No risk-stratified population
Interventions /Comparators and co-interventions	Pharmacological interventions† 12 or 13 hours oral corticosteroids with or without antihistamine 5–11 hours IV corticosteroids with or without antihistamine Any premedication less than 5 hours using corticosteroids, antihistamine or both Non-pharmacological interventions Change of CM that caused prior type B hypersensitivity reaction
Outcomes	Rates of acute (<1 hour) type B hypersensitivity reactions‡ Acute reaction-related deaths within 30 days Severe reactions only Moderate and severe reactions only Upgraded reactions compared with the index reactions All hypersensitivity reactions Rates of adverse events induced by preventive interventions
Predictors of acute adverse reactions	Patient-level characteristics Prior type B hypersensitivity reactions Prior type A physiologic reactions§ Allergic diathesis (eg, asthma, food or drug allergy, etc) Intervention-level characteristics Types and regimens of interventions Dosing of specific premedication drugs Change of CM (specific class/product and/or dosing)
Designs	Any study designs including at least 10 patients Randomised controlled trials Non-randomised trials Prospective and retrospective cohorts Comparative (two or more-group) design Single-group design

*Per-study defined risk criteria are allowed.
†Both guideline-recommended and ad-hoc regimens are allowed, but will be analysed separately. Guideline-recommended oral regimens are defined as follows2: 13 hours regimen: prednisone 50 mg PO at 13, 7 and 1 hours before CM injection+/−optional diphenhydramine 50 mg IV, IM or PO at 1 hour before CM injection; 12 hours regimen: methylpredonisolone 32 mg PO at 12 and 2 hours before CM injection+/−optional antihistamine. Guideline-recommended urgent regimens are: methylprednisolone 40 mg or hydrocortisone 200 mg IV every 4 hours until CM injection (minimum cumulative duration 5 hours)+/−diphenhydramine 50 mg IV at 1 hour before CM injection. Any premedication that does not include corticosteroids or that is less than 5 hours in duration is non-standard.
‡Grades of type B hypersensitivity reactions are defined as follows2: mild reactions include limited urticaria/pruritus, cutaneous oedema, limited ‘itchy’/‘scratchy’ throat, nasal congestion, sneezing, conjunctivitis and rhinorrhea; moderate reactions include diffuse urticaria/pruritus, diffuse erythema with stable vital signs, facial oedema without dyspnoea, throat tightness or hoarseness without dyspnoea, and wheezing/bronchospasm with mild or no hypoxia; and severe reactions include diffuse oedema, facial oedema with dyspnoea, diffuse erythema with hypotension, laryngeal oedema with stridor and/or hypoxia, wheezing/bronchospasm with significant hypoxia and anaphylactic shock (hypotension+tachycardia).
§Grades of type A physiologic reactions are defined as follows2: mild reactions include limited nausea/vomiting, transient flushing, warmth, chills, headache, dizziness, anxiety, altered taste, mild hypertension and vasovagal reaction that resolves spontaneously; moderate reactions include protracted nausea/vomiting, hypertensive urgency, isolated chest pain and vasovagal reaction that requires and is responsive to treatment; and severe reactions include vasovagal reaction resistant to treatment, arrhythmia, convulsions, seizures and hypertensive emergency.
CM, contrast medium; IM, intramuscularly; IV, intravenously; PICOD, populations, interventions, comparator interventions, outcomes and study designs; PO, orally.