Development and validation of case-finding algorithms for the identification of patients with anti-neutrophil cytoplasmic antibody-associated vasculitis in large healthcare administrative databases.
The aim of this study was to develop and validate case-finding algorithms for granulomatosis with polyangiitis (Wegener's, GPA), microscopic polyangiitis (MPA), and eosinophilic GPA (Churg-Strauss, EGPA).



Two hundred fifty patients per disease were randomly selected from two large healthcare systems using the International Classification of Diseases version 9 (ICD9) codes for GPA/EGPA (446.4) and MPA (446.0). Sixteen case-finding algorithms were constructed using a combination of ICD9 code, encounter type (inpatient or outpatient), physician specialty, use of immunosuppressive medications, and the anti-neutrophil cytoplasmic antibody type. Algorithms with the highest average positive predictive value (PPV) were validated in a third healthcare system.



An algorithm excluding patients with eosinophilia or asthma and including the encounter type and physician specialty had the highest PPV for GPA (92.4%). An algorithm including patients with eosinophilia and asthma and the physician specialty had the highest PPV for EGPA (100%). An algorithm including patients with one of the diagnoses (alveolar hemorrhage, interstitial lung disease, glomerulonephritis, and acute or chronic kidney disease), encounter type, physician specialty, and immunosuppressive medications had the highest PPV for MPA (76.2%). When validated in a third healthcare system, these algorithms had high PPV (85.9% for GPA, 85.7% for EGPA, and 61.5% for MPA). Adding the anti-neutrophil cytoplasmic antibody type increased the PPV to 94.4%, 100%, and 81.2% for GPA, EGPA, and MPA, respectively.



Case-finding algorithms accurately identify patients with GPA, EGPA, and MPA in administrative databases. These algorithms can be used to assemble population-based cohorts and facilitate future research in epidemiology, drug safety, and comparative effectiveness. Copyright © 2016 John Wiley & Sons, Ltd.
Vasculitis Center, Division of Rheumatology, University of Pennsylvania, Philadelphia, PA, USA.
Antoine G
AG
Sreih
Division of Rheumatology, Vanderbilt University Medical Center, Nashville, TN, USA.
Narender
N
Annapureddy
Division of Rheumatology, University of Kansas Medical Center, Kansas City, KS, USA.
Jason
J
Springer
The Vasculitis Foundation, Kansas City, MO, USA.
George
G
Casey
Division of Rheumatology, Vanderbilt University Medical Center, Nashville, TN, USA.
Kevin
K
Byram
Penn Medicine Academic Computing Services, University of Pennsylvania, Philadelphia, PA, USA.
Andy
A
Cruz
Division of Rheumatology, University of Kansas Medical Center, Kansas City, KS, USA.
Maya
M
Estephan
Penn Medicine Academic Computing Services, University of Pennsylvania, Philadelphia, PA, USA.
Vince
V
Frangiosa
Vasculitis Center, Division of Rheumatology, University of Pennsylvania, Philadelphia, PA, USA.
Michael D
MD
George
Division of Medical Informatics, Department of Internal Medicine, University of Kansas Medical Center, Kansas City, KS, USA.
Mei
M
Liu
Division of Rheumatology, University of Kansas Medical Center, Kansas City, KS, USA.
Adam
A
Parker
Vasculitis Center, Division of Rheumatology, University of Pennsylvania, Philadelphia, PA, USA.
Sapna
S
Sangani
Vasculitis Center, Division of Rheumatology, University of Pennsylvania, Philadelphia, PA, USA.
Rebecca
R
Sharim
Vasculitis Center, Division of Rheumatology, University of Pennsylvania, Philadelphia, PA, USA.|Department of Biostatistics and Epidemiology, University of Pennsylvania, Philadelphia, PA, USA.
Peter A
PA
Merkel
D000465:Algorithms; D056648:Anti-Neutrophil Cytoplasmic Antibody-Associated Vasculitis / Q000175:diagnosis / Q000453:epidemiology; D015267:Churg-Strauss Syndrome / Q000175:diagnosis* / Q000453:epidemiology; D016208:Databases, Factual / Q000706:statistics & numerical data; D014890:Granulomatosis with Polyangiitis / Q000175:diagnosis* / Q000453:epidemiology; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D038801:International Classification of Diseases; D055953:Microscopic Polyangiitis / Q000175:diagnosis* / Q000453:epidemiology; D011237:Predictive Value of Tests
D007166:Immunosuppressive Agents
ANCA; computable phenotypes; eosinophilic granulomatosis with polyangiitis; granulomatosis with polyangiitis; microscopic polyangiitis; pharmacoepidemiology; vasculitis