Administrative codes combined with medical records based criteria accurately identified bacterial infections among rheumatoid arthritis patients

J Clin Epidemiol. 2009 Mar;62(3):321-7, 327.e1-7. doi: 10.1016/j.jclinepi.2008.06.006. Epub 2008 Oct 1.


Objective: To evaluate diagnostic properties of International Classification of Diseases, Version 9 (ICD-9) diagnosis codes and infection criteria to identify bacterial infections among rheumatoid arthritis (RA) patients.

Study design and setting: We performed a cross-sectional study of RA patients with and without ICD-9 codes for bacterial infections. Sixteen bacterial infection criteria were developed. Diagnostic properties of comprehensive and restrictive sets of ICD-9 codes and the infection criteria were tested against an adjudicated review of medical records.

Results: Records on 162 RA patients with and 50 without purported bacterial infections were reviewed. Positive and negative predictive values of ICD-9 codes ranged from 54%-85% and 84%-100%, respectively. Positive predictive values of the medical records based criteria were 84% and 89% for "definite" and "definite or empirically treated" infections, respectively. Positive predictive value of infection criteria increased by 50% as disease prevalence increased using ICD-9 codes to enhance infection likelihood.

Conclusion: ICD-9 codes alone may misclassify bacterial infections in hospitalized RA patients. Misclassification varies with the specificity of the codes used and strength of evidence required to confirm infections. Combining ICD-9 codes with infection criteria identified infections with greatest accuracy. Novel infection criteria may limit the requirement to review medical records.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Aged
  • Arthritis, Rheumatoid / diagnosis*
  • Bacterial Infections / diagnosis*
  • Cross-Sectional Studies
  • Female
  • Forms and Records Control / standards
  • Humans
  • International Classification of Diseases / standards*
  • Male
  • Medical Records / standards
  • Middle Aged
  • Sensitivity and Specificity