Another variable of interest in the study by Reiss et al. (A-3) (see Exercise 9.3.4) was partial thromboplastin (aPTT), the standard test used to monitor heparin anticoagulation. Use the data in the following table to examine the correlation between aPTT levels as measured by the CoaguCheck point-of-care assay and standard laboratory hospital assay in 90 subjects receiving heparin alone, heparin with warfarin, and warfarin and exoenoxaparin.

Heparin Warfarin Warfarin and Exoenoxaparin CoaguCheck Hospital CoaguCheck Hospital CoaguCheck Hospital aPTT aPTT aPTT aPTT aPTT aPTT 49.3 71.4 18.0 77.0 56.5 46.5 57.9 86.4 31.2 62.2 50.7 34.9 59.0 75.6 58.7 53.2 37.3 28.0 77.3 54.5 75.2 53.0 64.8 52.3 42.3 57.7 18.0 45.7 41.2 37.5 44.3 59.5 82.6 81.1 90.1 47.1 90.0 77.2 29.6 40.9 23.1 27.1 55.4 63.3 82.9 75.4 53.2 40.6 20.3 27.6 58.7 55.7 27.3 37.8 28.7 52.6 64.8 54.0 67.5 50.4 64.3 101.6 37.9 79.4 33.6 34.2 90.4 89.4 81.2 62.5 45.1 34.8 64.3 66.2 18.0 36.5 56.2 44.2 89.8 69.8 38.8 32.8 26.0 28.2 74.7 91.3 95.4 68.9 67.8 46.3 150.0 118.8 53.7 71.3 40.7 41.0 32.4 30.9 128.3 111.1 36.2 35.7 20.9 65.2 60.5 80.5 60.8 47.2 89.5 77.9 150.0 150.0 30.2 39.7 44.7 91.5 38.5 46.5 18.0 31.3 61.0 90.5 58.9 89.1 55.6 53.0 36.4 33.6 112.8 66.7 18.0 27.4 52.9 88.0 26.7 29.5 18.0 35.7 57.5 69.9 49.7 47.8 78.3 62.0 39.1 41.0 85.6 63.3 75.3 36.7 74.8 81.7 68.8 43.5 73.2 85.3 32.5 33.3 18.0 54.0 42.0 38.3 125.7 142.9 92.6 100.5 49.3 39.8 77.1 98.2 46.2 52.4 22.8 42.3 143.8 108.3 60.5 93.7 35.8 36.0