Key result
The epinephrine test had a low positive predictive value of 6% for identifying a positive LQTS genotype, indicating it cannot be used alone to diagnose genotype-positive LQTS.
Why the study?
Does the epinephrine test predict genotype and guide management in children suspected of having congenital long QT syndrome?
Observational (n=41)
Yes
Does the epinephrine test predict genotype and guide management in children suspected of having congenital long QT syndrome?
The epinephrine test shows high discordance with genetic testing for diagnosing genotype-positive LQTS in children, but may still aid in clinical management decisions when combined with phenotype assessment.
Answers are grounded in this paper and cite their sources.
Caution against epinephrine test alone for pediatric LQTS genotyping; leaves open adjunctive role with phenotype assessment.
The epinephrine test has been shown to be a powerful tool to predict the genotype of congenital long QT syndrome (LQTS). The aim of this study was to evaluate its role in the diagnosis and management of LQTS in children. The test (using the Shimizu protocol) was conducted in patients with some evidence of LQTS but in whom clinical and management decisions were challenging (n = 41, age 9.6 +/- 3.9 years, 19 female). LQT1, LQT2, and negative responses to epinephrine were obtained in 16, 5, and 20 subjects, respectively. LQTS gene positivity was obtained in two subjects. Beta-blocker therapy was started in all subjects with a positive epinephrine response (n = 21) and in some negative responders because of their strong LQTS phenotype (n = 10). No therapy was given to the subset with less convincing features of LQTS who had also responded negatively to epinephrine (n = 10). Follow-up for 3.0 +/- 2 years was uneventful in both management groups. Due to the discordance with genotyping, the epinephrine test cannot be used to diagnose genotype-positive LQTS but when used in combination with phenotype assessment and genetic screening, it could enable better management decisions.
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Clur et al. (2009) conducted an observational in Suspected Congenital Long QT Syndrome (n=41). Epinephrine test was evaluated on Positive predictive value for LQTS genotype. The epinephrine test had a low positive predictive value of 6% for identifying a positive LQTS genotype, indicating it cannot be used alone to diagnose genotype-positive LQTS.
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