# QT prolongation risk factors and a monitoring strategy in rifampicin-resistant tuberculosis: Findings from the STREAM Stage 2 trial

## TL;DR

This study identifies risk factors for QT interval prolongation in patients with rifampicin-resistant tuberculosis and evaluates a monitoring strategy to detect it.

## Contribution

The study provides new insights into risk factors and a monitoring strategy for QT interval prolongation in RR-TB treatment.

## Key findings

- QT/QTcF ≥500ms occurred in 6.9% of the 9-month control group, 3.8% of the 9-month oral group, and 4.2% of the 6-month group.
- Higher baseline QTcF and geographical region were significantly associated with increased odds of QT/QTcF ≥500ms.
- The monitoring strategy showed high sensitivity and negative predictive value in identifying patients at risk.

## Abstract

Treatment of rifampicin-resistant tuberculosis (RR-TB) involves drugs that can prolong the QT interval. There is limited data on risk factors and the level of cardiac monitoring required. We analysed STREAM Stage 2 data to address these issues. A post-hoc analysis was undertaken of data from participants allocated to 3 regimens: 9-month control (n = 202), 9-month oral (n = 211) and 6-month (n = 143). Risk factors for development of a QT or QTcF (corrected QT interval [Fredericia’s formula]) interval ≥500ms were assessed. The diagnostic accuracy of a monitoring strategy for QT/QTcF prolongation was tested. QT/QTcF ≥ 500ms occurred on all regimens: 9-month control (n = 14 (6.9%)), 9-month oral (n = 8 (3.8%)) and 6-month (n = 6 (4.2%)). The participating country with the highest number of QT/QTcF interval ≥500ms events was Mongolia (18 events [64%]). A higher baseline QTcF was significantly associated with development of QT/QTcF ≥ 500ms (OR 1.05; 95% CI 1.03 to 1.07, p < 0.001). There was a suggested association between moxifloxacin (compared to levofloxacin, OR 2.49; 95% CI 0.92 to 6.71, p = 0.07) and a higher baseline TSH (OR 3.52; 95% CI 0.84 to 14.73, p = 0.08) and increased odds of QT/QTcF ≥ 500ms. The monitoring strategy performed well in the control (sensitivity 100%; specificity 62%; positive predictive value (PPV) 13% and negative predictive value (NPV) 100%) and oral (sensitivity 100%, specificity 59%, PPV 6% and NPV 100%) regimen groups. Baseline QTcF and geographical region were associated with increased odds of QT/QTcF prolongation. The monitoring strategy performed well in the identification of participants at higher risk of QT/QTcF prolongation.