Diagnostic reproducibility of epinephrine drug challenge interpretation in suspected long QT syndrome

Introduction The epinephrine challenge has been proposed to improve the diagnosis of congenital long QT syndrome (LQTS). The aim of the study was to evaluate the diagnostic reliability of the epinephrine provocative test for LQTS diagnosis, taking into consideration intra- and interobserver variability in the interpretation of the test. Methods and Results A retrospective analysis of 79 consecutive epinephrine provocative tests was conducted. Epinephrine was administered following a standardized protocol at two doses: 0.05 and 0.10 mu g kg(-1) min(-1). Electrocardiograms were blindly read twice by three different operators at >= 1-week interval. QT and RR intervals were collected at rest and at each dose, as well as final operator interpretation of the test. There was a high interobserver reproducibility of corrected QT measurements with an intraclass correlation (ICC) of 0.74 (95% confidence interval, 0.66-0.80) but a low interobserver reproducibility on the final interpretation with a kappa of 0.31. Intraobserver reproducibility of corrected QT was very good (ICC 0.93; 0.91-0.95), but still resulted in an only moderate intraobserver reproducibility in the final diagnosis (kappa of 0.47). Perceived certainty of at least 1 reading by 2 operators (N = 62 tests) increased interobserver reproducibility compared with baseline (kappa = 0.43). Conclusion Inter- and intraobserver agreement in the interpretation of the epinephrine provocation test for LQTS is poor to modest. Complexity in interpretation varies from one case to the next. The low reliability of this test encourages a reconsideration of its importance in the clinical management of patients with suspected LQTS.