Letter by Kaufman Regarding Article, “Closer Look at Genetic Testing in Long-QT Syndrome: Will DNA Diagnostics Ever Be Enough?”
To the Editor:
In his editorial, “Closer Look at Genetic Testing in Long-QT Syndrome: Will DNA Diagnostics Ever Be Enough?,”1 Dr MacRae categorizes genotyping as having no additional benefit in patients who meet clinical criteria for long-QT syndrome. I would like to point out that if the family mutation is unknown, genotyping such patients can be very useful. Knowledge of the long-QT syndrome subtype can help the clinician stratify risk and identify the therapy most likely to be protective. The different genetic subtypes of long-QT syndrome (ie, LQT1, LQT2, and LQT3) have different clinical outcomes and respond differently to various treatments.2,3 The informed clinician can judge when β-blocker medication is adequate and when an implantable cardioverter-defibrillator is required to prevent sudden cardiac death.
A second point that deserves emphasis is that genetic testing in borderline phenotype individuals with a known family mutation can be of great value. A negative test identifies those who do not require further testing and treatment, whereas a positive test leads to appropriate follow-up of vulnerable individuals.