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June 2008

Savvy Coder: Coding & Reimbursement
Some Rules of Thumb for Your Diagnostic Dilemmas, Part Two
By Gordon E. Johns, MD, and Sue Vicchrilli, COT, OCT, Academy Coding Executive

Getting reimbursed for a service requires the use of two coding systems. You use the CPT codes to describe the services provided and the ICD-9-CM codes to describe why those services were medically necessary. These codes are also known as the “procedural” and “diagnostic” codes, respectively.

In the vast majority of cases, it is obvious which diagnostic code applies—but when you’re unsure, there are some general principles that you can apply. Last month, I described three of those rules of thumb, and here are four more.

Rule 4. Do not code conditions that no longer exist. In applying this rule, you must ask yourself two questions: When does the condition no longer exist, and how do you prove medical necessity if the condition is no longer present? Suppose, for instance, a patient returns to see you for follow-up of conjunctivitis, but the conjunctivitis has now resolved. Can you use the appropriate conjunctivitis code? In this case, yes. The reason for the encounter is clearly the conjunctivitis that the patient experienced. Using this code establishes medical necessity. However, six months later when the same patient returns for a routine check of her contact lenses, it would then be inappropriate to use the conjunctivitis code. There are no rules or guidelines for what constitutes an acceptable period of time. Therefore, you will have to use your best judgment.

Rule 5. Always match the diagnostic code (ICD-9-CM) with the procedural code (CPT-4). All carriers use specific edits to make sure what we are doing is medically necessary. It makes little sense to them to pay for a cataract surgery when the diagnosis is something other than cataract. Failure to follow this guideline is much more frequently a matter of inattention to details rather than ignorance of the guidelines.

Rule 6. Assign codes to conditions not found in ICD-9-CM. Fortunately, you won’t often be faced with an unusual disease or circumstance that is not listed in ICD-9-CM. But when this does happen, there are three steps to follow: First, know the pathophysiology of the condition; second, know the organization, conventions and rules of ICD-9-CM; and third, manually search the most likely section of ICD-9-CM.

If you have a syndrome that has multiple manifestations, you would choose the one that most clearly justifies the visit to your office.

For some conditions, billers may need significant help to understand the pathophysiology, and the doctor can be a key resource. While you may be acquainted with the more common eye codes (360–379), a familiarity with other sections of ICD-9-CM is invaluable. Consider the sections on congenital anomalies (740–759), infectious diseases (000–139), neoplasm (140–239) and injury and poisoning (800–999), which includes many options for surgical complications.

Finally, there is no substitute for simply opening the ICD-9-CM book to the most likely section and manually searching all the available codes.

Rule 7. Remember your insurance carrier’s version of the golden rule: He who has the gold makes the rules. If the carrier requests that you follow certain protocol, it would be best to follow their advice, even if they do not follow proper coding rules or conventions.

For Part One, see last month’s Savvy Coder at


MEET THE EXPERT. Dr. Johns edits the AAOE’s ICD-9 for Ophthalmology, which lists the codes for a large number of unusual conditions that don’t appear in the standard ICD-9-CM texts (look for the 2008 edition, product #012264, at

At this year’s Joint Meeting, he will present “ICD-9: Coding the Common and the Complex” (Instruction course #433). Starting on June 25, Academy and AAOE members can register and buy course tickets at