Volume 148, Issue 6, Pages 1447-1453 (December 2015) Ordering of the Serum Angiotensin-Converting Enzyme Test in Patients Receiving Angiotensin-Converting Enzyme Inhibitor Therapy  Matthew D. Krasowski, MD, PhD, Johanna Savage, MD, Alexandra Ehlers, BS, Jon Maakestad, BS, Gregory A. Schmidt, MD, FCCP, Sonia La'ulu, BS, Natalie N. Rasmussen, BS, Frederick G. Strathmann, PhD, Jonathan R. Genzen, MD, PhD  CHEST  Volume 148, Issue 6, Pages 1447-1453 (December 2015) DOI: 10.1378/chest.15-1061 Copyright © 2015 The American College of Chest Physicians Terms and Conditions

Figure 1 ACE levels in patients at University of Iowa. A, ACE activities in patients receiving an ACE inhibitor (n = 108) vs not receiving an ACE inhibitor (n = 1,184). P «i .001 between the two groups by Mann-Whitney U test. B, Distribution of ACE activities indicating percentage of patients receiving an ACE inhibitor within each category. ACE = angiotensin-converting enzyme. CHEST 2015 148, 1447-1453DOI: (10.1378/chest.15-1061) Copyright © 2015 The American College of Chest Physicians Terms and Conditions

Figure 2 Distribution of patient results from 70,000 consecutive ACE assays at the national reference laboratory. A, Female results. B, Male results. Data are displayed in 2-U/L bin increments. Results below the assay analytical measurement range (> 5 U/L) are shown in the leftmost, isolated vertical bar in each graph; x-axes are cropped at 100 U/L. See Figure 1 legend for expansion of abbreviation. CHEST 2015 148, 1447-1453DOI: (10.1378/chest.15-1061) Copyright © 2015 The American College of Chest Physicians Terms and Conditions

Figure 3 Concentration-response relationships of three common ACE inhibitors on ACE assay activity. Inhibition of ACE activity by increasing concentrations of lisinopril (⋄), enalaprilat (•), and captopril (□) is shown. Symbol and error bars indicate mean ± SD. The ACE assay is the one used by ARUP Laboratories. Laboratories Figure 1 legend for expansion of abbreviation. CHEST 2015 148, 1447-1453DOI: (10.1378/chest.15-1061) Copyright © 2015 The American College of Chest Physicians Terms and Conditions