Field 24E - the Diagnosis Pointer field confuses a lot of people. Basically, if you have multiple diagnoses and multiple procedures to bill for the patient you have to tell the insurance which diagnosis resulted in which procedure. That is where Field 24E comes into play.
The purpose of this field is to "point", or associate, the CPT procedure code used in Field 24D with the appropriate ICD diagnosis code in Field 21 A through L. It is not where you enter the ICD diagnosis code itself but you indicate which one is pertinent to the procedure code on this particular line.
If you only have one ICD 10 diagnosis code in Field 21 then Field 24E will be "A" without the brackets. If you have three diagnosis codes in Field 21 - A, B & C, then Field 24E could be A or B or C or a combination of them (Except when billing Medicare - see below).
Here are the parameters as defined by the NUCC:
In 24E, enter the diagnosis code reference letter (pointer) as shown in Item Number 21 to relate the date of service and the procedures performed to the primary diagnosis. When multiple services are performed, the primary reference letter for each service should be listed first, other applicable services should follow. The reference letter(s) should be A – L or multiple letters as applicable. ICD-10-CM or ICD-9-CM diagnosis codes must be entered in Item Number 21. Do not enter them in 24E.
Enter letters left justified in the field. Do not use commas between the letters.
Please note that Medicare's instructions are a bit different:
Item 24E - This is a required field. Enter the diagnosis code reference number or letter (as appropriate, per form version) as shown in item 21 to relate the date of service and the procedures performed to the primary diagnosis. Enter only one reference number/letter per line item. When multiple services are performed, enter the primary reference number/letter for each service.
If a situation arises where two or more diagnoses are required for a procedure code (e.g., pap smears), the provider shall reference only one of the diagnoses in item 21.