Accuracy of ICD-9-CM codes in identifying reportable communicable diseases

Area of Science:

• Public Health
• Medical Informatics
• Healthcare Administration

Background:

• Accurate identification of communicable diseases is crucial for public health surveillance.
• Outpatient billing records are increasingly used for disease tracking.
• The International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) is a standard coding system.

Purpose of the Study:

• To evaluate the accuracy of using outpatient billing data and ICD-9-CM codes to identify reportable communicable diseases.
• To assess the specificity of this method in an academic medical center setting.

Main Methods:

• Billing records from an outpatient university medical center were screened for communicable diseases.
• Patient charts were reviewed to verify the accuracy of identified cases.
• The accuracy of ICD-9-CM coding for 20 specific communicable diseases was assessed.

Main Results:

• Thirty-three percent of identified communicable disease cases were found to be incorrectly coded.
• A significant lack of specificity was observed, indicating numerous false positives.
• Encounter form data combined with ICD-9-CM codes demonstrated poor accuracy for disease identification.

Conclusions:

• Relying solely on outpatient billing data and ICD-9-CM codes for communicable disease surveillance is unreliable.
• Improvements in coding specificity and data validation are necessary for accurate public health reporting.
• This study highlights the limitations of using administrative data for clinical disease identification.