ABSTRACT
A Combination Code is a single code used to classify two diagnoses, or a diagnosis with an associated manifestation or complication. Combination Codes pose difficulties that did not exist in International Classification of Diseases, 9th Revision (ICD-9) because they represent multiple codes in ICD-9, or codes that include manifestations and complications. Combination Codes appear throughout ICD-10. Providers should try to identify them for their practices in order to preclude problems associated with using General Equivalency Mapping (GEM) tools in converting ICD-9 codes to ICD-10 codes. The Alphabetic Index of Diseases will indicate combination codes by referring to subterm entries. Combination Codes clearly demonstrate problems in using GEM tools to convert ICD-9 codes to ICD-10 codes. A review of ICD-10 shows that there are a great number of Combination Codes. Diabetes mellitus codes are generally in subcategory E08-E13; however, there is a major exception for diabetes mellitus when it occurs in pregnant women.
