ECG monitoring in STREAM Stage 1: can we identify those at increased risk of QT prolongation?

BACKGROUND: STREAM (Standardised Treatment Regimen of Anti-tuberculosis Drugs for Patients with Multidrug-resistant Tuberculosis) Stage 1 was a randomised trial of a Short (9-month) regimen for rifampicin-resistant TB (RR-TB). QT or QTcF prolongation ≥500 ms occurred in 31 (11%) of 282 Short regimen participants. The frequent ECG monitoring employed might be challenging for treatment programmes. This analysis aimed to determine whether those at higher risk of severe QT prolongation could be identified early for more targeted monitoring.METHODS: Data from the first month of treatment were used to investigate whether participants were at risk of developing QT/QTcF ≥500 ms. QTcF increases from baseline at different time points were examined. Absolute QTcF measurements were categorised in 5 ms increments at each time-point. The most discriminating time points and QTcF cut-offs were combined to optimise sensitivity and specificity.RESULTS: Absolute QTcF values were more discriminating than magnitude of increase from baseline. More participants who developed QT/QTcF ≥500 ms had a QTcF of respectively ≥425 ms and ≥430 ms at 4 h and Week 3 (P < 0.05) than those who did not. By combining QTcF values ≥425 ms at 4 h and ≥430 ms at Week 3, we identified high-risk participants with 97% sensitivity and 99% negative predictive value.CONCLUSION: Reduced ECG monitoring may be possible for many Short regimen participants.