ICD-9 codes and surveillance for Clostridium difficile-associated disease

Area of Science:

• Medical Diagnostics
• Infectious Disease Epidemiology
• Health Informatics

Background:

• Clostridium difficile-associated disease (CDAD) is a significant healthcare-associated infection.
• Accurate identification and surveillance of CDAD are crucial for effective management and prevention.
• Current methods for determining CDAD rates include laboratory toxin assays and administrative diagnostic codes.

Purpose of the Study:

• To compare the accuracy of International Classification of Diseases, 9th Revision (ICD-9) codes versus C. difficile-toxin assays for identifying CDAD.
• To evaluate the correlation, sensitivity, and specificity of ICD-9 codes in diagnosing CDAD.

Main Methods:

• Retrospective cohort study design.
• Comparison of CDAD case ascertainment using C. difficile-toxin assay results.
• Analysis of CDAD case ascertainment using ICD-9 diagnostic codes.
• Statistical analysis including correlation coefficient (K) and calculation of sensitivity and specificity.

Main Results:

• A good correlation was observed between C. difficile-toxin assay results and ICD-9 codes (K = 0.72, p<0.01).
• The sensitivity of ICD-9 codes for detecting CDAD was 78%.
• The specificity of ICD-9 codes for detecting CDAD was 99.7%.

Conclusions:

• International Classification of Diseases, 9th Revision (ICD-9) codes demonstrate a strong agreement with C. difficile-toxin assays for CDAD surveillance.
• ICD-9 codes represent a highly specific and reasonably sensitive tool for epidemiological monitoring of CDAD.
• These findings support the utility of ICD-9 codes in public health surveillance of Clostridium difficile infections.