Validity of ICD-9-CM Coding for Identifying Incident Methicillin-Resistant Staphylococcus aureus (MRSA) Infections

Is MRSA Infection Coded as a Chronic Disease?

In medical administrative databases, the International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) administrative code for methicillin-resistant Staphylococcus aureus (MRSA) is V09. An examination of the validity of using the V09 code to identify MRSA infections found that V09 does not accurately predict the rate of MRSA infections and should not be used to analyze it.

The authors assessed data for all adults admitted to three hospitals in different states between January 1, 2001 and December 31, 2007. They examined records of MRSA-positive clinical cultures during hospitalization, calculating the k statistic to measure how often the V09 code was assigned to the MRSA infection cases, including sensitivities, specificities and positive and negative predictive values.

Of the 4,506 discharged patients who were assigned the V09 code; 31 percent had an incident MRSA infection, 20 percent had a history of MRSA infection but not an infection during the index hospitalization; and 49 percent had no record of MRSA infection. The V09 code identified MRSA infection with 24 percent sensitivity, positive predictive value of 31 percent. Agreement between the MRSA-positive patients and those also assigned the V09 code had a k coefficient of 0.26.

The authors suggest that creating a new system of recording MRSA infections could lead to more accurate data on MRSA rates and outcomes.