Validation of continuous QTc measurement in critically ill patients.

INTRODUCTION: Prolongation of the corrected QT interval (QTc) can lead to torsades de pointes. This study is designed to determine the validity of the continuous QTc (cQTc) measurement in critically ill patients. METHODS: In a retrospective cohort study, QTc analysis was performed with manual measurements on a single selected lead from a 12-lead ECG and cQTc measurement obtained at the same time. In addition, automated QTc measurement from the 12-lead ECG was also included in the study. Validation was performed by calculating intraclass correlation coefficient (ICC), Pearson's correlation and Bland-Altman plot. RESULTS: 119 patients with QRS<120 ms were included with a mean cQTc of 468 ms (standard deviation (SD) 37) and mean manually measured QTc of 449 ms (SD 41) (p<0.001). Pearson's correlation was 0.65 (p<0.01), ICC was 0.65 (95% CI: 0.53-0.74). Bland-Altman plot shows a mean difference of 19.5 ms (limits of agreement (LOA) -44.6 to 83.7). For cQTc compared to automated QTc from the 12-lead ECG the intraclass correlation coefficient was 0.77 (95% CI: 0.68-0.83, p<0.001) and the Bland-Altman plot shows a mean difference of 7.8 ms (LOA -40.2 to 55.8). CONCLUSION: cQTc measurement in critically ill patients with a QRS duration shorter than 120 ms shows an acceptable accuracy to be used in routine care.

Two ankle joint laxity testers: reliability and validity.

Two test devices were manufactured to objectively measure ankle joint laxity: the dynamic anterior ankle tester (DAAT) and the quasi-static anterior ankle tester (QAAT). The primary aim was to analyse the reliability of both testers; The secondary aim was to assess validity in correlation with TELOS stress test and manual anterior drawer test. Twenty-four normal subjects and 14 patients 1 year after acute lateral ankle ligament injury were included. Both ankles were tested with the DAAT and QAAT by two different observers; one experienced orthopaedic surgeon performed the manual test; the TELOS stress X-rays were evaluated by one observer. Intra observer reliability for the DAAT varied between 0.81 and 0.94; for the QAAT between 0.71 and 0.94. Inter observer reliability for the DAAT varied between 0.84 and 0.94; for the QAAT between 0.76 and 0.82. Concurrent validity showed fair correlation between DAAT and QAAT for the first couple observers (0.71); however, a poor correlation was observed for the second couple (0.42). No significant correlations were found between neither DAAT and the TELOS and the manual test, nor QAAT and the TELOS and the manual test. In conclusion, reliability of both testers is high. Validity of the testers needs further investigation.