Processing Requirements

The hospital must follow the procedure described below for each error code. For bills returned to the provider, the A/B MAC (A) considers the bill improperly completed for control and processing time purposes.

NOTE: The following instructions are based on ICD-9-CM diagnosis and procedure codes. Applicable ICD-10-CM and ICD-10-PCS codes will be provided as part of the annual updates when ICD-10 is implemented. 

1. Invalid Diagnosis or Procedure Code 

The MCE checks each diagnosis code, including the admitting diagnosis, and each procedure code against a table of valid diagnosis and procedure codes. An admitting diagnosis, a principle diagnosis, and up to eight additional diagnoses may be reported. Up to six total procedure codes may be reported on an inpatient claim. If the recorded code is not in this table, the code is invalid, and the A/B MAC (A) returns the bill to the provider. 

For a list of valid diagnosis or procedure codes see the "International Classification of Diseases” revision applicable to the date of the inpatient discharge or other service and the "Addendum/Errata" and new codes furnished by the A/B MAC (A). The hospital must review the medical record and/or face sheet and enter the correct diagnosis/procedure codes before returning the bill.

2. External Cause of Injury Code as Principal Diagnosis 

External Cause of Injury codes describe the circumstances that caused an injury, not the nature of the injury, and therefore are not recognized by the Grouper program as acceptable principal diagnoses. In ICD-9-CM the external cause of injury diagnosis codes begin with the letter E. In ICD-10-CM the external cause of injury codes begin with the letters V, W, X and Y. For a list of all External cause of injury codes, see "International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM), January 1979, Volume l (Diseases)" and the International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM). The hospital must review the medical record and/or face sheet and enter the correct diagnosis before returning the bill.

3. Duplicate of PDX 

Any secondary diagnosis that is the same code as the principal diagnosis is identified as a duplicate of the principal diagnoses. This is unacceptable because the secondary diagnosis may cause an erroneous assignment to a higher severity MS-DRG. Hospitals may not repeat a diagnosis code. The A/B MAC (A) will delete the duplicate secondary diagnosis and process the bill.

4. Age Conflict

The MCE detects inconsistencies between a patient's age and any diagnosis on the patient's record. Examples are:

 • A 5-year-old patient with benign prostatic hypertrophy. 

• A 78-year-old delivery. 

In the above cases, the diagnosis is clinically impossible in a patient of the stated age. Therefore, either the diagnosis or age is presumed to be incorrect. Four age code categories are described below.

• A subset of diagnoses is intended only for newborns and neonates. These are "Newborn" diagnoses. For "Newborn" diagnoses, the patient's age must be 0 years. 

• Certain diagnoses are considered reasonable only for children between the ages of 0 and 17. These are "Pediatric" diagnoses. 

• Diagnoses identified as "Maternity" are coded only for patients between the ages of l2 and 55 years.

• A subset of diagnoses is considered valid only for patients over the age of 14. These are "Adult" diagnoses. For "Adult" diagnoses the age range is 15 through 124.