Long QT syndrome in children: the value of rate corrected QT interval and DNA analysis as screening tests in the general population.
OBJECTIVE
To evaluate two hypothetical screening strategies for identifying children with long QT syndrome (LQTS), a cause of sudden death in childhood.


METHODS
Families with KVLQT1, HERG, or SCN5A genotypes provided electrocardiographic (ECG) data for this analysis. This is the first time such genotype-phenotype information has been available. Using the LQTS genotype, the distributions of QTc in affected and unaffected children were established and screening performance for various QTc cut off points were modelled. The detection rate for DNA mutation analysis was determined from published experience.


RESULTS
The mean QTc (SD) was 0.484 seconds (0.031) in 117 affected children and 0.420 seconds (0.021) in 133 unaffected children. A QTc cut off of 0.50 seconds in a population of 1 million children would identify 61 of the 200 affected children, and 100 unaffected children. Estimates of testing costs for a screening programme in the newborn period would be $327 869/case detected and $2 222 000/death avoided. Although not presently available for routine use, DNA analysis could, theoretically, identify 100 of the 200 children with LQTS within the same population, along with an estimated 100 unaffected children.


CONCLUSIONS
The only available screening test for LQTS is ECG measurement. If DNA technology becomes available for screening, unit costs must be very low to be competitive. There are multiple problems with screening for LQTS: only a minority of children will be detected, cost/death avoided is high, and pilot studies would need to be in place for 5-10 years to document efficacy.
Allan
W C
WC
Foundation for Blood Research, PO Box 190, 69 US Route One, Scargborough, ME 04070-0190, USA. allan@fbr.org
Timothy
K
K
Vincent
G M
GM
Palomaki
G E
GE
Neveux
L M
LM
Haddow
J E
JE
D000293:Adolescent; D027682:Cation Transport Proteins; D002648:Child; D002675:Child, Preschool; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins; D000072237:ERG1 Potassium Channel; D004562:Electrocardiography; D051638:Ether-A-Go-Go Potassium Channels; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D051656:KCNQ Potassium Channels; D051657:KCNQ1 Potassium Channel; D008133:Long QT Syndrome / Q000175:diagnosis* / Q000235:genetics*; D008297:Male; D008403:Mass Screening / Q000379:methods*; D062554:NAV1.5 Voltage-Gated Sodium Channel; D010375:Pedigree; D015221:Potassium Channels / Q000235:genetics; D024642:Potassium Channels, Voltage-Gated; D015222:Sodium Channels / Q000235:genetics; D015534:Trans-Activators; D000071230:Transcriptional Regulator ERG
D027682:Cation Transport Proteins; D004268:DNA-Binding Proteins; C072312:ERG protein, human; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human; C092509:KCNH6 protein, human; D051656:KCNQ Potassium Channels; D051657:KCNQ1 Potassium Channel; C496909:KCNQ1 protein, human; D062554:NAV1.5 Voltage-Gated Sodium Channel; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; C568320:SCN5A protein, human; D015222:Sodium Channels; D015534:Trans-Activators; D000071230:Transcriptional Regulator ERG