Fig 4.

Diagnostic accuracy of a universal, low‐molecular‐weight heparin (LMWH)‐calibrated anti‐Xa assay for the measurement of rivaroxaban, apixaban, and edoxaban drug concentrations as determined in a multicentre cross‐sectional study in clinical practice (n = 867). (A) Box plots illustrating the distribution of measurements (median, interquartile range, minimum to maximum, all results) at clinically relevant cut‐offs (> and < 30, 50, and 100 µg/l). (B) Receiver‐operating characteristic (ROC) curves showing the diagnostic accuracy. The area under the ROC curve was 0·99 for all cut‐offs. (C) Confusion matrices at each cut‐off. Drug levels of >30 µg/l were detected with a sensitivity of 96·2% (95% CI 94·4–97·4; cut‐off value 0·35 u/ml), drug levels of >50 µg/l with a sensitivity of 96·4% (95% CI 94·4–97·7; cut‐off value 0·58 u/ml) and drug levels of >100 µg/l with a sensitivity of 96·4% (95% CI 94·0–97·9; cut‐off value 1·14 u/ml). The specificities were 92·9% (95% CI 88·9–95·5), 93·3% (95% CI 90·1–95·5) and 92·0 (95% CI 89·4–94·0) respectively.