Clinical codes combined with procedure codes increase diagnostic accuracy of Crohn's disease in a US Military health record.

The poor PPV of ICD-9-CM codes in making the diagnosis of CD should be taken into consideration when interpreting results and when conducting research using such codes. Limiting these codes to those patients who have been given this diagnosis by a gastroenterologist, or to those who have had a colonoscopy near the time of diagnosis, increases the PPV.