Reassessing the role of QT(c) in the diagnosis of autonomic failure among patients with diabetes: A meta-analysis

Abstract

OBJECTIVE - A 1992 consensus statement on autonomic testing portrayed Bazett's heart rate-corrected QT interval (QT(c)) prolongation as a specific yet insensitive indicator of diabetic autonomic failure. At that time, only a few small studies had evaluated the accuracy of QT(c). To date, even fewer studies have evaluated whether its accuracy is influenced by patient characteristics. RESEARCH DESIGN AND METHODS - We critically appraised 17 studies reporting the sensitivity and specificity of QT(c) for diabetic autonomic failure. The studies represented 4,584 patients with diabetes (mean age 34.9 years, 46% female, 92% with type 1 diabetes, mean duration of diabetes 14.5 years). We summarized the accuracy of QT(c) prolongation for diabetic autonomic failure as an odds ratio (OR) (95% CI) and determined whether patient and study design characteristics influenced the accuracy of QT(c) prolongation by comparing summary receiver operating characteristic curves. RESULTS - Autonomic failure, defined as≥1.2 ± 0.4 (mean ± SD) abnormal of 2.0 ±1.6 administered cardiovascular reflex tests, was found in 26% (25-28) of patients. The pooled sensitivity and specificity of QT(c) > 441 ± 8 ms for autonomic failure were 28% (26-29) and 86% (85-87), respectively. Autonomic failure was 2.26 times (1.90-2.70) more likely to be present in patients with than in patients without QT prolongation. At 86% specificity, the sensitivity of QT(c) prolongation was 46 vs. 12% for men versus women (P = 0.0077), respectively, and, after adjustment for sex, 66 vs. 17% among patients aged 25 vs. 55 years (P = 0.1902) and 61 vs. 27% at thresholds of >420 vs. >460 ms, respectively (P = 0.2964). CONCLUSIONS - QT(c) prolongation is a specific albeit insensitive indicator of autonomic failure. Although QT(c) prolongation is relatively accurate for men, accuracy may be even greater for young men at low QT(c) thresholds.