Walking the Fine Line of Crosswalks: Understanding ICD-9-CM Vol. 3 vs. CPT-4

Vol. 15 •Issue 7 • Page 14
CCS Prep!

Walking the Fine Line of Crosswalks: Understanding ICD-9-CM Vol. 3 vs. CPT-4

Whenever the phrase “procedure coding” is mentioned, the first question many outpatient coders have is “CPT or ICD-9?” And even though HIPAA guidelines dictate that for hospital coding the ICD-9-CM volume 3 code set is for inpatient visits only and the CPT code set is for outpatient services only, in reality, many hospitals still require their outpatient coders to assign both sets of codes for outpatient visits. This is for a variety of reasons: in some cases the HIM staff needs to access data across service lines and visit types and so require that all procedural services be coded in ICD-9-CM. Of course, the vast majority of payers now require CPT coding for outpatient services, so hospital coders have become extremely proficient in this system as well.

But what happens when coders try to “crosswalk” between the systems? Crosswalking is starting with an already assigned code in one system and then using that information to link to the other system without starting over in the logic stream. While crosswalking is extremely efficient and helpful in many cases, the coder must be aware of certain pitfalls involved in indiscriminate crosswalking. This is not to say that coders should avoid crosswalks, but they should be aware of the hazards and inherent weaknesses in any crosswalked system.

The first step is understanding that the two systems are inherently different. CPT was developed with the medical staff in mind and services are more closely related to those provided by a physician. ICD-9 (particularly the Clinical Modification-CM version used in the United States) includes many services that are provided in a hospital setting, which in some cases reflects non-invasive but still codable procedures. When two such disparate systems are asked to match up, sometimes the result is less than optimal! We’re asking the two systems to match to something that in some cases it was never intended to match.

Coders should keep in mind that in many cases there is not a one-to-one ratio between the systems. For surgical services, CPT is typically more specific and will provide many more codes for a given type of service than ICD-9-CM. The most common example is that of laceration suturing. For the majority of skin and subcutaneous suturing services, one ICD-9-CM code (86.59) is assigned. But the same service may be coded from a much larger group of available codes in CPT, based upon which site of the body is repaired, and the extent (depth) of the suturing. This is why more specific information is required for appropriate CPT code assignment. Never try to assign CPT codes based solely on ICD-9-CM procedure codes; in many cases an inappropriate or non-specific code will result. Information that indicates only “excision of a skin lesion” (ICD-9-CM code 86.3) will not crosswalk appropriately to a CPT code, which relies on further information, such as the morphology of the lesion (benign or malignant) and the site from which the excision was taken.

In some cases ICD-9-CM codes exist for services provided in the hospital setting for which there are no corresponding CPT codes. Examples include: indwelling catheter irrigation (96.48), removal of foreign body without incision (98.2X) and pelvic exam without anesthesia (89.26). But be aware that the reverse may also be true. A good example of this relates to burn treatment. Simple small burn treatment, such as that typically provided in the hospital’s emergency department (ED), is assigned to code 16020 (Dressings and/or debridement; initial or subsequent; without anesthesia, office or hospital; small). But to assign the appropriate ICD-9-CM procedure code, knowledge of the exact service provided is required because the code assignment is different depending on whether a debridement was provided, or merely a simple burn dressing.

Another problem with crosswalked codes is the issue of code terminology that doesn’t necessarily match or terms with different definitions. The accompanying table contains several examples of crosswalked codes that may reflect the same procedure but have very different code titles and/or definitions.

The coder must understand the underlying concepts behind ICD-9-CM vs. CPT as they relate to different definitions. For example, in case #2 within the table, foreign body (FB) removal from the foot may be coded in several different ways. If no incision is made and the FB is simply pulled from the foot with a forceps or hemostat, no CPT code would be assigned, because those codes assume and require that an incision be made for the procedure to be considered complex enough to assign a code. However, in ICD-9-CM code 98.28 may be assigned for an FB removal without incision. This is a good example of the lack of a one-to-one relationship or match between the two coding systems. In this case, only an ICD-9-CM code (98.28) would be assigned. Abstracting or other computerized systems must allow the coder to assign one code without the other in case of instances such as this. The coder must be aware of these guidelines when printed or electronic crosswalks present the full range of choices that include all of these codes. Just because a code appears on a crosswalk does not necessarily mean that it is the appropriate code assignment for every case documented.

In case #3 within the table, the issue in-volves toe amputations, and the CPT codes are specifically differentiated depending upon the exact location of the amputation, whether through the metatarsal at the metatarsophalangeal joint or at the interphalangeal joint. The coder should have access to this specific information before attempting to assign the correct code. But note that the ICD-9-CM procedure codes (84.11 and 84.12) are differentiated only by whether only the toe is amputated or the amputation is performed through the foot. There are some crosswalks that link CPT code 28810 (Amputation, metatarsal, with toe, single) to ICD-9-CM code 84.12 (Amputation through foot) because one of the inclusion terms under 84.12 is “transmetatarsal amputation.” But if the coder researches further and reviews Coding Clinic for ICD-9-CM, 4th Quarter 1999, p. 19, it’s indicated that in order to assign code 84.12, all toes must be amputated. Code 28810 reflects what’s typically documented as a “ray amputation” of a single toe with its corresponding metatarsal head. The Coding Clinic reference clearly directs the coder to ICD-9-CM code 84.11 for this service. There is also an EXCLUDES note under code 84.12 in the ICD-9-CM tabular for “Ray amputation of foot: 84.11.”

Coders should not make assumptions about the appropriateness of certain codes based solely on which chapter the code may reside. For example, refer to cases #4 and #5 in the table. Some coders assume that the only “invasive” or “surgical” types of CPT codes appear in the range between 10021 and 69990. But some invasive services, such as those performed on the cardiovascular system (including cardiac catheterization) reside in the “Medicine” section of CPT. These codes begin with the digit “9” but still may be a part of the HIM coding staff responsibilities. Likewise, some coders may feel that only non-invasive services are represented in Chapter 16 “Miscellaneous Diagnostic and Therapeutic Procedures” of ICD-9-CM Volume 3. But some services that actually do reflect invasive procedures are found here, including FB removal that in some cases necessitates an endoscopic approach.

To ensure that the most appropriate code is selected, the coder must also be well-versed in medical terminology. In example #6 in the table, if the coder was unaware that the talus bone was considered a tarsal bone, they might not realize that codes 77.98 and 28130 actually do reflect the same service.

In conclusion, although a crosswalk between ICD-9-CM and CPT is another tool in the coder’s arsenal, it should be used with full knowledge that it is not infallible and each code must be reviewed separately against the physician documentation for appropriateness. And coders that will be taking the certified coding specialist (CCS) exams should realize that no such access to any type of crosswalked materials will be available for use during the exam. It is necessary and advantageous to be capable of assigning both types of codes individually and independently from one another.

Test your knowledge of ICD-9-CM/CPT crosswalks with the quiz below:

1. The regulation that indicates which code sets are valid for each type of service provided in health care facilities today is:

a. Stark II



d. All of the above

2. Typically more specific information is necessary to code which of the following type of codes?

a. CPT

b. ICD-9-CM

c. Neither; they require the same level of detail in the documentation

d. HCPCS Level II

3. A patient with an indwelling Foley catheter has been having problems with keeping it clear and draining. He presents to the ED and catheter cleaning and irrigation is performed without replacing the catheter. The service is reported with the following procedure codes:

a. 51700; 96.47

b. 96.47 only

c. 96.48 only

d. 51702; 96.48

4. A 14-year-old male was fly fishing and accidentally got the fish hook stuck in the back of his hand. After being examined in the ED, the physician clipped the barbs off the protruding section of the fish hook and then pulled the hook out of the skin with a hemostat. The wound was irrigated, a dressing applied and the patient was discharged home. Which of the following codes would be appropriate for the case?

a. 98.26

b. 10120; 86.05

c. 20520; 98.26

d. 25248

5. A 9-year-old girl was bicycling with her family when she felt a foreign body enter her left eye, causing extreme irritation and pain. She was taken to the nearest ED, where a small foreign body was easily removed from her conjunctiva with a tweezers following irrigation. Which of the following codes would be appropriate for the case?

a. 98.21

b. 65210; 10.0

c. 65205; 98.21

d. 65270; 10.0

This month’s column has been prepared by Cheryl D’Amato, RHIT, CCS, director of HIM, and Melinda Stegman, MBA, CCS, manager of clinical HIM services, HSS Inc. (www.hssweb.com), which specializes in the development and use of software and e-commerce solutions for managing coding, reimbursement, compliance and denial management in the health care marketplace.

Answers to CCS PREP!: 1. b: HIPAA dictated use of ICD-9-CM volume 3 for inpatient procedures and CPT-4 for outpatient services for hospital-based coding; 2. a: Although there may be some limited examples of ICD-9-CM codes requiring more detail than CPT, the vast majority of CPT codes are more detailed and thus require a higher level of detail in the documentation to assign them appropriately; 3. c: Only code 96.48 (Irrigation of other indwelling urinary catheter) is assigned. The bladder itself was not irrigated so code 51700 is inappropriate and the Foley catheter was not replaced so code 51702 is also inappropriate; 4. a: No incision was made for this simple foreign body removal from the skin. Only ICD-9-CM 98.26 would be assigned. All other code choices require that an incision be made or that structures deeper than the skin be involved; 5. c: This was a simple superficial conjuctival foreign body removal and no incision was required. Codes 65205 and 98.21 are correct. Code 65210 reflects an embedded foreign body (not documented on this case) and 65270 requires that a laceration be repaired.

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