ICD-10 is a diagnostic coding system implemented by the World Health Organization (WHO) in 1993 to replace ICD-9, which was developed by WHO in the 1970s. ICD-10-CM is scheduled to replace ICD-9-CM, our current U.S. diagnostic code set, on Oct. 1, 2013. Medical science keeps making new discoveries, and there are no numbers to assign these diagnoses. ICD-9 is out of room because the classifications are organized scientifically and each three-digit category can have only 10 subcategories. Most numbers in most categories have been assigned diagnoses.
