title: Results of genetic testing in 855 consecutive unrelated patients referred for long QT syndrome in a clinical laboratory.
abstract: OBJECTIVE
  Our aim was to examine the diagnostic yield of genetic testing in 855 consecutive unrelated cases referred for Long QT syndrome (LQTS).
  
  
  RESULTS
  Eight hundred fifty five consecutive patients with a mean age at testing of 27.5±18.6 years, were referred for LQTS genetic testing and had accompanying clinical information. KCNQ1, KCNH2, SCN5A, ANK2, KCNE1, KCNE2, CACNA1C, KCNJ2, CAV3, and SCN4B were analyzed using Next-Generation sequencing in all patients, and 395 patients were also tested for an additional two genes, AKAP9 and SNTA1. We retrospectively analyzed the diagnostic yield of this genetic test and factors that predicted the likelihood of a disease causing mutation using ANOVA, χ2, t-test, and receiver operator curves. At least one mutation was identified in 30.3% of the patients (n=259), and 18 patients (2.1%) had two mutations. Patients with two mutations had a longer QTc interval (p<0.01) than patients with one mutation. A longer QTc duration and family history of LQTS were each associated with a higher yield of positive results on genetic testing (p<0.01 for each). Using a QTc cutoff of 476 msec or greater, the genetic testing had a sensitivity of 72% and a specificity of 49%. Mutations within the transmembrane domain of KCNQ1 were associated with a greater risk of cardiac arrest and syncope relative to mutations in other domains of the gene. Mutations in SCN5A were associated with a higher frequency of cardiac arrest (52.6%).
  
  
  CONCLUSIONS
  Sequencing-based genetic testing has a sensitivity of 72% and has clinical utility.
authors: Department of Pediatrics, Columbia University, New York, New York, USA.
authors: Krystien V
authors: KV
authors: Lieve
authors: Leah
authors: L
authors: Williams
authors: Amy
authors: A
authors: Daly
authors: Gabriele
authors: G
authors: Richard
authors: Sherri
authors: S
authors: Bale
authors: Daniela
authors: D
authors: Macaya
authors: Wendy K
authors: WK
authors: Chung
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D005260:Female; D020022:Genetic Predisposition to Disease; D005820:Genetic Testing / Q000379:methods*; D006323:Heart Arrest / Q000235:genetics; D006801:Humans; D051657:KCNQ1 Potassium Channel / Q000235:genetics; D008133:Long QT Syndrome / Q000175:diagnosis* / Q000235:genetics* / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009154:Mutation; D062554:NAV1.5 Voltage-Gated Sodium Channel / Q000235:genetics; D012680:Sensitivity and Specificity; D013575:Syncope / Q000235:genetics; D055815:Young Adult
chemical_list: D051657:KCNQ1 Potassium Channel; C496909:KCNQ1 protein, human; D062554:NAV1.5 Voltage-Gated Sodium Channel; C568320:SCN5A protein, human