Why Do We Need the General Equivalence Mappings?

*  ICD-10 is much more specific:

For diagnoses, there are 14,025 ICD-9-CM codes and 68,069 ICD-10-CM codes; and
For procedures, there are 3,824 ICD-9-CM codes and 72,589 ICD-10-PCS codes (in the 2009 versions of
ICD-9-CM, ICD-10-CM, and ICD-10-PCS).

*  One ICD-9-CM Diagnosis Code is represented by multiple ICD-10-CM codes:

 82002 Fracture of midcervical section of femur, closed

— From S72031A Displaced midcervical fracture of right femur, initial encounter for closed fracture

— From S72031G Displaced midcervical fracture of right femur, subsequent encounter for closed fracture with delayed healing

— From S72032A Displaced midcervical fracture of left femur, initial encounter for closed fracture

— From S72032G Displaced midcervical fracture of left femur, subsequent encounter for closed fracture with delayed healing

— And other codes from the GEMs
*  One ICD-10-CM Diagnosis Code is represented by multiple ICD-9-CM codes:

*  E11341 Type 2 diabetes mellitus with severe nonproliferative diabetic retinopathy
with macular edema
* To ICD-9 cluster:

— 25050 Diabetes with ophthalmic manisfestations, type II or specified type, not
stated as uncontrolled
— 36206 Severe nonproliferative diabetic retinopathy
— 36207 Diabetic macular edema

*  A few ICD-10-CM codes have no predecessor ICD-9-CM codes:

—  T500x6A Underdosing of mineralocorticoids and their antagonists, initial encounter
—  T501x6A Underdosing of loop [high-ceiling] diuretics, initial encounter
— T502x6A Underdosing of carbonic-anhydrase inhibitors, benzothiadiazides and other
diuretics, initial encounter
— T503x6A Underdosing of electrolytic, caloric and water-balance agents, initial
encounter
— T504x6A Underdosing of drugs affecting uric acid metabolism, initial encounter– And others found in the GEMs

*  One ICD-9-CM Procedure Code captured by multiple ICD-10-PCS codes:
8659 Suture of Skin and Subcutaneous Tissue of Other Sites
— To 0JQ10ZZ Repair Face Subcutaneous Tissue and Fascia, Open Approach
— To 0JQ13ZZ Repair Face Subcutaneous Tissue and Fascia, Percutaneous Approach
— To 0JQ40ZZ Repair Anterior Neck Subcutaneous Tissue and Fascia, Open Approach
— To 0JQ43ZZ Repair Anterior Neck Subcutaneous Tissue and Fascia,
Percutaneous Approach
— And others found in the GEMs