Recommendations	Consensus statement instruction	Ref.
Molecular genetic testing for definitive disease associated genes (currently KCNQ1, KCNH2, SCN5A, CALM1, CALM2, and CALM3) should be offered to all index patients with a high probability diagnosis of LQTS, based on examination of the patient’s clinical history, family history, and ECG characteristics obtained at baseline, during ECG Holter recording and exercise stress test (Schwartz Score ≥ 3.5, SupplementaryTable S2).a		20
Analysis of specific genes should be offered to patients with a specific diagnosis as follows: KCNQ1 and KCNE1 in patients with Jervell and Lange-Nielsen syndrome, CACNA1C in Timothy syndrome, KCNJ2 in Andersen–Tawil syndrome, and TRDN in patients suspected to have triadin knockout syndrome.		20, 89–93
An analysis of CACNA1C and KCNE1 may be performed in all index patients in whom a cardiologist has established a diagnosis of LQTS with a high probability, based on examination of the patient’s clinical history, family history, and ECG characteristics obtained at baseline, during ECG Holter recording and exercise stress test (Schwartz Score ≥ 3.5).a		20
Variant-specific genetic testing is recommended for family members and appropriate relatives following the identification of the disease-causing variant.		Expert opinion
Predictive genetic testing in related children is recommended from birth onward (any age).		Expert opinion

^aThe Schwartz score can be found in Supplementary material online, Table S2.