Refer to Exercise 9.7.2, which describes research by Reiss et al. (A-5), who collected samples from 90 patients and measured partial thromboplastin time (aPTT) using two different methods: the CoaguChek point-of-care assay and standard laboratory hospital assay. The subjects were also classified by their medication status: 30 receiving heparin alone, 30 receiving heparin with warfarin, and 30 receiving warfarin and enoxaparin. The data are as follows.

Heparin Heparin and Warfarin Warfarin and Enoxaparin CoaguChek aPTT Hospital aPTT CoaguChek aPTT Hospital aPTT CoaguChek aPTT Hospital 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 Source: Data provided courtesy of Curtis E. Haas, Pharm.D.

Use the multiple regression to predict the hospital aPTT from the CoaguCheck aPTT level as well as the medication received. Is knowledge of medication useful in the prediction? Let a ¼ :05 for all tests.