Beginning in 1997, the CPT directly addressed the concept of add-on codes by adding a note to the Surgical Guidelines section of the CPT book. These codes described services that would be done in addition to another service and did not require a -51 modifier. The note in CPT simply stated that add-on codes could be identified by nomenclature that said each additional or list separately in addition to primary procedure.
Ob/Gyn Add-On Coding Examples
In the ob/gyn section of CPT, for example, add-on codes made it possible to accurately report the biopsy of multiple lesions in an area without using the -51 modifier. If the physician performed a biopsy of a lesion on the vulva or perineum (56605), and also biopsied two additional lesions in the same region, the CPT provides a specific code, 56606 (biopsy of vulva or perineum; each separate additional lesion), to be added on or listed with the primary procedure. In this case, you would list code 56605 for the first lesion and the 56606 for each additional lesion (specify quantity in the units box of the claim form).
Another example of using an add-on code is in the case where a hysterectomy immediately follows a caesarean delivery. The c-section would be reported using the appropriate caesarean code (59510, 59514, 59515, 59618, 59620 or 59622), and then the hysterectomy would be reported using 59525.
The only other ob/gyn specific add-on code is 58611 (ligation or transection of fallopian tubes when done at the time of caesarean section or intra-abdominal surgery). This code would be reported in addition to the primary abdominal or caesarean surgery, again without a modifier.
1999 CPT Simplifies Add-On Codes
As stated previously, identification of add-on codes depended on the descriptive nomenclature, such as each additional or list separately in addition to primary procedure, but beginning in 1999, the CPT made identification easier. All add-on codes are preceded with the + symbol. For further identification, all add-on codes are listed in the summary Appendix E in the back of the CPT.
The 1999 CPT also has clarified that these codes
are for services provided by the same physician, stating: The add-on concept in CPT [...]