title: Ordering of the Serum Angiotensin-Converting Enzyme Test in Patients Receiving Angiotensin-Converting Enzyme Inhibitor Therapy: An Avoidable but Common Error.
abstract: BACKGROUND
  Serum angiotensin-converting enzyme (ACE) levels may be decreased by use of ACE inhibitor (ACEI) medication. In this study, we determined how often ACE levels were measured in patients receiving ACEI therapy.
  
  
  METHODS
  ACE levels analyzed over a 54-month preintervention time period at an academic medical center were reviewed retrospectively for tests performed during ACEI therapy. These data were compared with a large, deidentified dataset of ACE levels measured at a national reference laboratory; in vitro studies of ACEI inhibition; and liquid chromatography time-of-flight mass spectrometry detection of lisinopril in a subset of clinical specimens.
  
  
  RESULTS
  Over a 54-month period, 1,292 patients had ACE levels measured, with 108 patients (8.4%) receiving ACEI therapy at the time of testing. ACE levels measured for patients receiving ACEI therapy were substantially lower. In general, clinical teams did not recognize a medication effect on ACE levels. Introduction of a warning prompt in the electronic health record reduced the ordering of ACE levels in patients receiving ACEIs by > 60% in a 17-month postintervention time period. The deidentified dataset of ACE levels at a reference laboratory showed a bimodal distribution, with a peak of very low ACE levels. Using liquid chromatography time-of-flight mass spectrometry, the presence of lisinopril was confirmed in a subset of specimens with low ACE activity. In vitro studies of two different ACE assays showed significant inhibition of activity at clinically relevant concentrations.
  
  
  CONCLUSIONS
  Assessment of ACE activity is often measured for patients receiving ACEIs, potentially leading to low ACE concentrations and inaccurate interpretations.
authors.affiliation: Department of Pathology and the Department of Internal Medicine, University of Iowa, Iowa City, IA. Electronic address: mkrasows@healthcare.uiowa.edu.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Krasowski
authors.affiliation: Department of Pathology and the Department of Internal Medicine, University of Iowa, Iowa City, IA.
authors.forename: Johanna
authors.initials: J
authors.lastname: Savage
authors.affiliation: Department of Pathology and the Department of Internal Medicine, University of Iowa, Iowa City, IA.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Ehlers
authors.affiliation: Department of Pathology and the Department of Internal Medicine, University of Iowa, Iowa City, IA.
authors.forename: Jon
authors.initials: J
authors.lastname: Maakestad
authors.affiliation: Department of Pathology and the Department of Internal Medicine, University of Iowa, Iowa City, IA.
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Schmidt
authors.affiliation: ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT.
authors.forename: Sonia
authors.initials: S
authors.lastname: La'ulu
authors.affiliation: ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT.
authors.forename: Natalie N
authors.initials: NN
authors.lastname: Rasmussen
authors.affiliation: ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT; Department of Pathology, University of Utah, Salt Lake City, UT.
authors.forename: Frederick G
authors.initials: FG
authors.lastname: Strathmann
authors.affiliation: ARUP Institute for Clinical and Experimental Pathology, Salt Lake City, UT; Department of Pathology, University of Utah, Salt Lake City, UT.
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Genzen
mesh_terms: D000328:Adult; D000368:Aged; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000493:pharmacokinetics / Q000627:therapeutic use; D001682:Biological Availability; D002318:Cardiovascular Diseases / Q000188:drug therapy; D003951:Diagnostic Errors / Q000517:prevention & control / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D017706:Lisinopril / Q000493:pharmacokinetics / Q000627:therapeutic use; D008297:Male; D008875:Middle Aged; D007703:Peptidyl-Dipeptidase A / Q000032:analysis / Q000097:blood; D012189:Retrospective Studies; D012507:Sarcoidosis / Q000097:blood* / Q000175:diagnosis; D014481:United States
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D017706:Lisinopril; D007703:Peptidyl-Dipeptidase A