Table 4 Summary of population screening studies of long QT syndrome

Number of unrelated index cases (n)

262

541

430

169

2500

200

Detection rate (%) All cases/more stringent criteria (*Schwartz score ≥ 4)

51

50/72*

72

32/71

36

52

Novel mutations (%)

60

59

59

54

60

28

Multiple mutations (%)

-

10

5

0

9

4

Mutated gene:

KCNQ1 (%)

39

42

49

43

43

58

KCNH2 (%)

51

42

39

46

32

24

SCN5A (%)

6

15

10

9

13

13

KCNE1 (%)

2

0.5

2

2

3

1

KCNE2 (%)

2

0.5

1

-

1

1

RYR2 (%)

-

- 269/6^a

-

- 41/17

-

3 36/8

RYR2 (n/%)

Mutation type:

Missense (%)

72

73

72

65

70

70

Nonsense (%)

6

6

5

14

6

8

In-frame ins/del (%)

5

2

14

3

3

5

Frame shift (%)

10

12

6

13

15

12.5

Splice site (%)

7

6

3

5

6

1.5

Large ins/del (%)

-

-

-

-

-

3

Mutation region:

N-terminal (%)

22

16

8

22

8

25

Transmembrane (%)

54

49

64

54

57

47

C-terminal (%)

24

35

28

24

35

28