Table 1. Open in new tab Patient...

	Development cohort	Validation cohort
Sex, male	39 (100.0%)	502 (100.0%)		11 (100.0%)	36 (100.0%)
Age, y	34.7 ± 8.4	47.1 ± 10.5	< .001	35.9 ± 7.8	52.8 ± 13.1	< .001
ECG-K⁺, mEq/L				2.6 ± 0.6	3.0 ± 0.5	.106
Weakness	39(100.0%)	50(10.0%)	< .001	11(100.0%)	36(100.0%)
ECG morphology
Heart rate	95.1 ± 17.5	91.5 ± 21.7	.306	100.0 ± 10.1	85.3 ± 14.6	.003
PR interval	176.0 ± 33.2	162.1 ± 37.1	.025	166.1 ± 57.3	166.6 ± 40.5	.674
QRS duration	101.6 ± 10.8	102.3 ± 17.9	.806	96.5 ± 11.1	110.2 ± 26.0	.094
QT interval	384.3 ± 76.0	395.1 ± 55.8	.257	364.6 ± 29.3	399.2 ± 47.4	.023
Correct QT interval	476.1 ± 81.2	480.0 ± 50.4	.662	470.2 ± 43.2	471.4 ± 46.0	1.000
P waves axes	65.0 ± 60.6	54.8 ± 30.7	.074	51.5 ± 68.6	53.1 ± 32.4	.905
RS waves axes	57.2 ± 23.3	47.5 ± 49.6	.227	47.9 ± 28.7	47.4 ± 35.9	.950
T waves axes	47.5 ± 79.9	42.8 ± 63.5	.670	17.7 ± 50.8	49.3 ± 77.3	.407
Laboratory test
TSH, μIU/mL	0.0 ± 0.1	1.3 ± 1.2	< .001	0.0 ± 0.0	1.8 ± 1.4	.004
Free T4, ng/dL	2.5 ± 0.6	1.0 ± 0.3	< .001	2.7 ± 0.5	1.1 ± 0.1	.003
eGFR, mL/min	146.2 ± 54.6	90.4 ± 59.5	< .001	156.1 ± 43.7	91.3 ± 45.6	< .001
Cr, mg/dL	0.8 ± 0.6	1.7 ± 2.3	.019	0.7 ± 0.2	1.6 ± 2.3	< .001
BUN, mg/dL	18.0 ± 15.2	18.8 ± 15.5	.748	11.7 ± 3.7	19.9 ± 16.3	.117
K⁺, mEq/L	2.5 ± 0.6	2.8 ± 0.2	< .001	2.5 ± 0.5	2.7 ± 0.3	.027
Na⁺, mEq/L	139.2 ± 2.2	136.1 ± 5.0	< .001	139.3 ± 1.2	137.6 ± 5.0	.454
Cl^–, mEq/L	106.7 ± 2.3	99.4 ± 7.6	< .001	108.0 ± 2.1	101.3 ± 7.4	.005
Ca⁺⁺, mg/dL	8.8 ± 0.7	8.5 ± 0.8	.024	8.9 ± 0.6	8.1 ± 0.9	.003
Mg⁺⁺, mg/dL	1.9 ± 0.3	1.9 ± 0.4	.334	2.0 ± 0.2	1.8 ± 0.5	.541

Development cohort

Validation cohort

TPP (n = 39)

HypoK control (n = 502)

TPP (n = 11)

non-TPP (n = 36)

Sex, male

39 (100.0%)

502 (100.0%)

11 (100.0%)

36 (100.0%)

Age, y

34.7 ± 8.4

47.1 ± 10.5

< .001

35.9 ± 7.8

52.8 ± 13.1

< .001

ECG-K⁺, mEq/L

2.6 ± 0.6

3.0 ± 0.5

.106

Weakness

39(100.0%)

50(10.0%)

< .001

11(100.0%)

36(100.0%)

ECG morphology

Heart rate

95.1 ± 17.5

91.5 ± 21.7

.306

100.0 ± 10.1

85.3 ± 14.6

.003

PR interval

176.0 ± 33.2

162.1 ± 37.1

.025

166.1 ± 57.3

166.6 ± 40.5

.674

QRS duration

101.6 ± 10.8

102.3 ± 17.9

.806

96.5 ± 11.1

110.2 ± 26.0

.094

QT interval

384.3 ± 76.0

395.1 ± 55.8

.257

364.6 ± 29.3

399.2 ± 47.4

.023

Correct QT interval

476.1 ± 81.2

480.0 ± 50.4

.662

470.2 ± 43.2

471.4 ± 46.0

1.000

P waves axes

65.0 ± 60.6

54.8 ± 30.7

.074

51.5 ± 68.6

53.1 ± 32.4

.905

RS waves axes

57.2 ± 23.3

47.5 ± 49.6

.227

47.9 ± 28.7

47.4 ± 35.9

.950

T waves axes

47.5 ± 79.9

42.8 ± 63.5

.670

17.7 ± 50.8

49.3 ± 77.3

.407

Laboratory test

TSH, μIU/mL

0.0 ± 0.1

1.3 ± 1.2

< .001

0.0 ± 0.0

1.8 ± 1.4

.004

Free T4, ng/dL

2.5 ± 0.6

1.0 ± 0.3

< .001

2.7 ± 0.5

1.1 ± 0.1

.003

eGFR, mL/min

146.2 ± 54.6

90.4 ± 59.5

< .001

156.1 ± 43.7

91.3 ± 45.6

< .001

Cr, mg/dL

0.8 ± 0.6

1.7 ± 2.3

.019

0.7 ± 0.2

1.6 ± 2.3

< .001

BUN, mg/dL

18.0 ± 15.2

18.8 ± 15.5

.748

11.7 ± 3.7

19.9 ± 16.3

.117

K⁺, mEq/L

2.5 ± 0.6

2.8 ± 0.2

< .001

2.5 ± 0.5

2.7 ± 0.3

.027

Na⁺, mEq/L

139.2 ± 2.2

136.1 ± 5.0

< .001

139.3 ± 1.2

137.6 ± 5.0

.454

Cl^–, mEq/L

106.7 ± 2.3

99.4 ± 7.6

< .001

108.0 ± 2.1

101.3 ± 7.4

.005

Ca⁺⁺, mg/dL

8.8 ± 0.7

8.5 ± 0.8

.024

8.9 ± 0.6

8.1 ± 0.9

.003

Mg⁺⁺, mg/dL

1.9 ± 0.3

1.9 ± 0.4

.334

2.0 ± 0.2

1.8 ± 0.5

.541

	Development cohort	Validation cohort
Sex, male	39 (100.0%)	502 (100.0%)		11 (100.0%)	36 (100.0%)
Age, y	34.7 ± 8.4	47.1 ± 10.5	< .001	35.9 ± 7.8	52.8 ± 13.1	< .001
ECG-K⁺, mEq/L				2.6 ± 0.6	3.0 ± 0.5	.106
Weakness	39(100.0%)	50(10.0%)	< .001	11(100.0%)	36(100.0%)
ECG morphology
Heart rate	95.1 ± 17.5	91.5 ± 21.7	.306	100.0 ± 10.1	85.3 ± 14.6	.003
PR interval	176.0 ± 33.2	162.1 ± 37.1	.025	166.1 ± 57.3	166.6 ± 40.5	.674
QRS duration	101.6 ± 10.8	102.3 ± 17.9	.806	96.5 ± 11.1	110.2 ± 26.0	.094
QT interval	384.3 ± 76.0	395.1 ± 55.8	.257	364.6 ± 29.3	399.2 ± 47.4	.023
Correct QT interval	476.1 ± 81.2	480.0 ± 50.4	.662	470.2 ± 43.2	471.4 ± 46.0	1.000
P waves axes	65.0 ± 60.6	54.8 ± 30.7	.074	51.5 ± 68.6	53.1 ± 32.4	.905
RS waves axes	57.2 ± 23.3	47.5 ± 49.6	.227	47.9 ± 28.7	47.4 ± 35.9	.950
T waves axes	47.5 ± 79.9	42.8 ± 63.5	.670	17.7 ± 50.8	49.3 ± 77.3	.407
Laboratory test
TSH, μIU/mL	0.0 ± 0.1	1.3 ± 1.2	< .001	0.0 ± 0.0	1.8 ± 1.4	.004
Free T4, ng/dL	2.5 ± 0.6	1.0 ± 0.3	< .001	2.7 ± 0.5	1.1 ± 0.1	.003
eGFR, mL/min	146.2 ± 54.6	90.4 ± 59.5	< .001	156.1 ± 43.7	91.3 ± 45.6	< .001
Cr, mg/dL	0.8 ± 0.6	1.7 ± 2.3	.019	0.7 ± 0.2	1.6 ± 2.3	< .001
BUN, mg/dL	18.0 ± 15.2	18.8 ± 15.5	.748	11.7 ± 3.7	19.9 ± 16.3	.117
K⁺, mEq/L	2.5 ± 0.6	2.8 ± 0.2	< .001	2.5 ± 0.5	2.7 ± 0.3	.027
Na⁺, mEq/L	139.2 ± 2.2	136.1 ± 5.0	< .001	139.3 ± 1.2	137.6 ± 5.0	.454
Cl^–, mEq/L	106.7 ± 2.3	99.4 ± 7.6	< .001	108.0 ± 2.1	101.3 ± 7.4	.005
Ca⁺⁺, mg/dL	8.8 ± 0.7	8.5 ± 0.8	.024	8.9 ± 0.6	8.1 ± 0.9	.003
Mg⁺⁺, mg/dL	1.9 ± 0.3	1.9 ± 0.4	.334	2.0 ± 0.2	1.8 ± 0.5	.541

Table 1.

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Patient characteristics in the development and validation cohorts

	Development cohort			Validation cohort
	TPP (n = 39)	HypoK control (n = 502)	P	TPP (n = 11)	non-TPP (n = 36)	P
Sex, male	39 (100.0%)	502 (100.0%)		11 (100.0%)	36 (100.0%)
Age, y	34.7 ± 8.4	47.1 ± 10.5	< .001	35.9 ± 7.8	52.8 ± 13.1	< .001
ECG-K⁺, mEq/L				2.6 ± 0.6	3.0 ± 0.5	.106
Weakness	39(100.0%)	50(10.0%)	< .001	11(100.0%)	36(100.0%)
ECG morphology
Heart rate	95.1 ± 17.5	91.5 ± 21.7	.306	100.0 ± 10.1	85.3 ± 14.6	.003
PR interval	176.0 ± 33.2	162.1 ± 37.1	.025	166.1 ± 57.3	166.6 ± 40.5	.674
QRS duration	101.6 ± 10.8	102.3 ± 17.9	.806	96.5 ± 11.1	110.2 ± 26.0	.094
QT interval	384.3 ± 76.0	395.1 ± 55.8	.257	364.6 ± 29.3	399.2 ± 47.4	.023
Correct QT interval	476.1 ± 81.2	480.0 ± 50.4	.662	470.2 ± 43.2	471.4 ± 46.0	1.000
P waves axes	65.0 ± 60.6	54.8 ± 30.7	.074	51.5 ± 68.6	53.1 ± 32.4	.905
RS waves axes	57.2 ± 23.3	47.5 ± 49.6	.227	47.9 ± 28.7	47.4 ± 35.9	.950
T waves axes	47.5 ± 79.9	42.8 ± 63.5	.670	17.7 ± 50.8	49.3 ± 77.3	.407
Laboratory test
TSH, μIU/mL	0.0 ± 0.1	1.3 ± 1.2	< .001	0.0 ± 0.0	1.8 ± 1.4	.004
Free T4, ng/dL	2.5 ± 0.6	1.0 ± 0.3	< .001	2.7 ± 0.5	1.1 ± 0.1	.003
eGFR, mL/min	146.2 ± 54.6	90.4 ± 59.5	< .001	156.1 ± 43.7	91.3 ± 45.6	< .001
Cr, mg/dL	0.8 ± 0.6	1.7 ± 2.3	.019	0.7 ± 0.2	1.6 ± 2.3	< .001
BUN, mg/dL	18.0 ± 15.2	18.8 ± 15.5	.748	11.7 ± 3.7	19.9 ± 16.3	.117
K⁺, mEq/L	2.5 ± 0.6	2.8 ± 0.2	< .001	2.5 ± 0.5	2.7 ± 0.3	.027
Na⁺, mEq/L	139.2 ± 2.2	136.1 ± 5.0	< .001	139.3 ± 1.2	137.6 ± 5.0	.454
Cl^–, mEq/L	106.7 ± 2.3	99.4 ± 7.6	< .001	108.0 ± 2.1	101.3 ± 7.4	.005
Ca⁺⁺, mg/dL	8.8 ± 0.7	8.5 ± 0.8	.024	8.9 ± 0.6	8.1 ± 0.9	.003
Mg⁺⁺, mg/dL	1.9 ± 0.3	1.9 ± 0.4	.334	2.0 ± 0.2	1.8 ± 0.5	.541

	Development cohort			Validation cohort
	TPP (n = 39)	HypoK control (n = 502)	P	TPP (n = 11)	non-TPP (n = 36)	P
Sex, male	39 (100.0%)	502 (100.0%)		11 (100.0%)	36 (100.0%)
Age, y	34.7 ± 8.4	47.1 ± 10.5	< .001	35.9 ± 7.8	52.8 ± 13.1	< .001
ECG-K⁺, mEq/L				2.6 ± 0.6	3.0 ± 0.5	.106
Weakness	39(100.0%)	50(10.0%)	< .001	11(100.0%)	36(100.0%)
ECG morphology
Heart rate	95.1 ± 17.5	91.5 ± 21.7	.306	100.0 ± 10.1	85.3 ± 14.6	.003
PR interval	176.0 ± 33.2	162.1 ± 37.1	.025	166.1 ± 57.3	166.6 ± 40.5	.674
QRS duration	101.6 ± 10.8	102.3 ± 17.9	.806	96.5 ± 11.1	110.2 ± 26.0	.094
QT interval	384.3 ± 76.0	395.1 ± 55.8	.257	364.6 ± 29.3	399.2 ± 47.4	.023
Correct QT interval	476.1 ± 81.2	480.0 ± 50.4	.662	470.2 ± 43.2	471.4 ± 46.0	1.000
P waves axes	65.0 ± 60.6	54.8 ± 30.7	.074	51.5 ± 68.6	53.1 ± 32.4	.905
RS waves axes	57.2 ± 23.3	47.5 ± 49.6	.227	47.9 ± 28.7	47.4 ± 35.9	.950
T waves axes	47.5 ± 79.9	42.8 ± 63.5	.670	17.7 ± 50.8	49.3 ± 77.3	.407
Laboratory test
TSH, μIU/mL	0.0 ± 0.1	1.3 ± 1.2	< .001	0.0 ± 0.0	1.8 ± 1.4	.004
Free T4, ng/dL	2.5 ± 0.6	1.0 ± 0.3	< .001	2.7 ± 0.5	1.1 ± 0.1	.003
eGFR, mL/min	146.2 ± 54.6	90.4 ± 59.5	< .001	156.1 ± 43.7	91.3 ± 45.6	< .001
Cr, mg/dL	0.8 ± 0.6	1.7 ± 2.3	.019	0.7 ± 0.2	1.6 ± 2.3	< .001
BUN, mg/dL	18.0 ± 15.2	18.8 ± 15.5	.748	11.7 ± 3.7	19.9 ± 16.3	.117
K⁺, mEq/L	2.5 ± 0.6	2.8 ± 0.2	< .001	2.5 ± 0.5	2.7 ± 0.3	.027
Na⁺, mEq/L	139.2 ± 2.2	136.1 ± 5.0	< .001	139.3 ± 1.2	137.6 ± 5.0	.454
Cl^–, mEq/L	106.7 ± 2.3	99.4 ± 7.6	< .001	108.0 ± 2.1	101.3 ± 7.4	.005
Ca⁺⁺, mg/dL	8.8 ± 0.7	8.5 ± 0.8	.024	8.9 ± 0.6	8.1 ± 0.9	.003
Mg⁺⁺, mg/dL	1.9 ± 0.3	1.9 ± 0.4	.334	2.0 ± 0.2	1.8 ± 0.5	.541

Abbreviations: BUN, blood urea nitrogen; Ca⁺⁺, total calcium; Cl^–, chloride; Cr, creatinine; ECG, electrocardiography; ECG-K⁺, K⁺ estimated via electrocardiography; eGFR, estimated glomerular filtration rate; Free T4, free thyroxine; HypoK, hypokalemia; K⁺, potassium; Mg⁺⁺, magnesium; Na⁺, sodium; TSH, thyrotropin; TPP, thyrotoxic periodic paralysis.

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