Evaluation of International Classification of Diseases, Ninth Revision, Clinical Modification Codes for reporting methicillin-resistant Staphylococcus aureus infections at a hospital in Illinois

Infect Control Hosp Epidemiol. 2010 May;31(5):463-8. doi: 10.1086/651665.


Background: States, including Illinois, have passed legislation mandating the use of International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes for reporting healthcare-associated infections, such as methicillin-resistant Staphylococcus aureus (MRSA).

Objective: To evaluate the sensitivity of ICD-9-CM code combinations for detection of MRSA infection and to understand implications for reporting.

Methods: We reviewed discharge and microbiology databases from July through August of 2005, 2006, and 2007 for ICD-9-CM codes or microbiology results suggesting MRSA infection at a tertiary care hospital near Chicago, Illinois. Medical records were reviewed to confirm MRSA infection. Time from admission to first positive MRSA culture result was evaluated to identify hospital-onset MRSA (HO-MRSA) infections. The sensitivity of MRSA code combinations for detecting confirmed MRSA infections was calculated using all codes present in the discharge record (up to 15); the effect of reviewing only 9 diagnosis codes, the number reported to the Centers for Medicare and Medicaid Services, was also evaluated. The sensitivity of the combination of diagnosis codes for detection of HO-MRSA infections was compared with that for community-onset MRSA (CO-MRSA) infections.

Results: We identified 571 potential MRSA infections with the use of screening criteria; 403 (71%) were confirmed MRSA infections, of which 61 (15%) were classified as HO-MRSA. The sensitivity of MRSA code combinations was 59% for all confirmed MRSA infections when 15 diagnoses were reviewed compared with 31% if only 9 diagnoses were reviewed (P < .001). The sensitivity of code combinations was 33% for HO-MRSA infections compared with 62% for CO-MRSA infections (P < .001).

Conclusions: Limiting analysis to 9 diagnosis codes resulted in low sensitivity. Furthermore, code combinations were better at revealing CO-MRSA infections than HO-MRSA infections. These limitations could compromise the validity of ICD-9-CM codes for interfacility comparisons and for reporting of healthcare-associated MRSA infections.

Publication types

  • Evaluation Study

MeSH terms

  • Cross Infection / diagnosis*
  • Cross Infection / epidemiology
  • Cross Infection / microbiology
  • Databases, Factual
  • Disease Notification / legislation & jurisprudence
  • Disease Notification / standards*
  • Hospitals / standards*
  • Hospitals / statistics & numerical data
  • Humans
  • Illinois / epidemiology
  • International Classification of Diseases / standards*
  • International Classification of Diseases / statistics & numerical data*
  • Medical Records
  • Methicillin-Resistant Staphylococcus aureus / classification
  • Methicillin-Resistant Staphylococcus aureus / isolation & purification*
  • Patient Discharge / standards
  • Patient Discharge / statistics & numerical data
  • Staphylococcal Infections / diagnosis*
  • Staphylococcal Infections / epidemiology
  • Staphylococcal Infections / microbiology
  • United States