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Reviewing the fundamentals can strengthen your ICD-9 coding and streamline the reimbursement process.

Fam Pract Manag. 1999;6(7):27-31

When you talk about the work you do and the conditions you see, you use words — patient visit, suture, Pap smear, sinusitis. When third-party payers refer to the work you do and the conditions you see, they use numbers. Almost every medical condition, service and supply can be identified by a numeric code, primarily because Medicare and other third-party payers require numeric coding on claim forms. They set the payment rules, so they also get to establish the system's “vocabulary.”

Being fluent in the language of coding may not be every doctor's dream. But accurate coding is the key to prompt reimbursement for your services. It's helpful even in environments dominated by managed care, giving you a database you can use in practice profiling and contract negotiations. In addition, the codes you submit are used by the federal government to ferret out health care fraud. So knowing the difference between a diagnosis code of 280 (iron deficiency anemia) and 820 (a fracture of the neck of the femur) will help protect your practice from fraud and abuse investigations, as well as help ensure that you get paid for what you do. Consequently, it's more important than ever that you take a moment to brush up your coding skills and improve your coding accuracy.

Elsewhere in this issue, you'll find a tool to help you choose the right CPT code for more-involved evaluation and management services (see “A Quick-Reference Card for Identifying Level-4 Visits”). In this article, you'll get a refresher in the language of coding symptoms and diagnoses.

ICD-9 vs. CPT

Reimbursement claims actually require the use of two coding systems: one that identifies the patient's disease or physical state (the International Classification of Diseases, 9th Revision, Clinical Modification, or ICD-9-CM, codes) and another that describes the procedures, services or supplies you provide to your patients (the Current Procedural Terminology, or CPT, codes). To differentiate between these coding systems, think of it this way: CPT codes describe what you do, and ICD-9 codes describe why you do it.

Each service you provide becomes a line item (a CPT code) on an insurance claim form. Although your level of reimbursement is linked to a claim's CPT codes, you need to record a symptom, diagnosis or complaint (an ICD-9 code) to establish the “medical necessity” of each service. Showing medical necessity basically means that you justify your treatment choice (CPT code) by linking it to an appropriate diagnosis, symptom or complaint (ICD-9 code). Up to four ICD-9 codes can be linked to each CPT code on a HCFA-1500 form.

For example, a patient in the office for routine diabetes monitoring also complains of chest pain suggesting angina pectoris. As part of the work-up that day, you perform an ECG in your office. On your claim form, however, you list only the ICD-9 code for diabetes. In all likelihood, the insurer won't pay for the ECG because it's not clear from the claim form why the test was medically necessary. The ICD-9 code for chest pain or angina pectoris should also have been listed to indicate the medical necessity for the ECG.

General guidelines for ICD-9 coding

  • Code to the highest degree of specificity. Carry the code to the fourth or fifth digit when possible.

  • Link the diagnosis code (ICD-9) to the service code (CPT) on the insurance claim form to identify why the service was rendered, thereby establishing medical necessity.

  • “Ruled out,” “suspected,” and “probable” diagnoses cannot be coded. Assign the applicable code for the sign or symptom that is the reason for the patient visit.

  • Code the primary diagnosis first, followed by the secondary, tertiary, etc., diagnoses. The primary diagnosis is the main reason for the patient visit.

  • Code coexisting conditions that affect the patient's treatment in that visit. Code chronic conditions when they apply to the patient's treatment. Don't code diagnoses that are no longer being treated or that don't affect your care of the patient.

Finding ICD-9 codes

ICD-9 codes are organized in three “volumes,” which aren't necessarily separate publications, and are available in a variety of print and electronic formats (the codes themselves are in the public domain). Volume I is a numeric listing of the roughly 12,000 diagnostic codes and descriptions (give or take a few!). Volume II is an alphabetic index of terms and the codes that correspond to them; its more than 120,000 entries direct you to the codes you need by linking them to a variety of terms. Volume III contains a tabular list and alphabetic index of procedural codes and descriptions and is intended for use only by hospitals. Always look in the index first and then turn to the numeric listing for a complete description of the condition. Never code solely from the index.

Using the right digits

ICD-9 codes may have three to five digits depending on their category (although only a few diagnoses have valid three-digit codes). Each digit provides important information about the patient's condition. For example, consider the following codes in the diabetes mellitus category:

  • 250, diabetes mellitus;

  • 250.1, diabetes with ketoacidosis;

  • 250.13, uncontrolled type 1 diabetes with ketoacidosis.

The three-digit code (in this case, 250) represents the diagnostic category. The fourth digit identifies complications associated with diabetes (e.g., ketoacidosis). The fifth digit describes the type of diabetes and its level of control. To correctly code an encounter with a patient who has uncontrolled type 1 diabetes complicated by ketoacidosis, you should use all five digits.

Here's another example: You see a patient for follow-up of benign essential hypertension. The proper code would be 401.1 The fourth digit identifies the disease as benign and thus is the most specific description of your patient's condition. If, however, the patient also had benign hypertensive heart disease, then you would include a fifth digit: The proper code would be 402.10 or 402.11 depending on the absence or presence, respectively, of congestive heart failure.

The point is that you must always code to the highest number of digits that best describe your patient's condition. To be certain you're using the correct number of digits, review the codes in a given category and choose the highest-level code that most specifically describes your patient's condition. Many payers, including Medicare, will deny or delay payments if you fail to do so.

FPM resources for ICD-9 coding

A useful tool for ICD-9 coding is Family Practice Management'sICD-9 Codes for Family Practice,” compiled by Allen Daugird, MD, MBA, and Donald Spencer, MD, MBA, of the Department of Family Medicine, University of North Carolina. The list includes many of the ICD-9 codes family physicians use most often, organized alphabetically within categories of diseases and body systems. A version of the list printed on cardstock, designed to be carried with you as you see patients or to be placed in each exam room, is available from the AAFP Order Department at 800-944-0000. Ask for item number A512 (for two copies) or A513 (for 10 copies).

For more information on ICD-9 coding, review these articles from the FPM archives:

In addition, watch for an ICD-9 update this fall in FPM, once the code changes for 1999-2000 are announced.

Should I code suspected diagnoses?

Choosing the most specific code means coding only what you know to be a fact. Patients often have ill-defined complaints, such as back pain. While you may suspect a specific condition —perhaps a herniated disc or a urinary tract infection — and then order lab tests to confirm the diagnosis, you should code only the sign or symptom that brought the patient in to see you until you receive the test results or otherwise make a definitive diagnosis. (See “ICD-9 coding challenges” for an example.) If you don't, you may inadvertently label the patient with an incorrect diagnosis and, as a result, the patient may have difficulty obtaining health and disability insurance or may end up paying higher insurance premiums in the future.

Use ICD-9 codes 780 to 789 to describe symptoms, signs and ill-defined conditions that aren't linked to a specific disease. But be aware that some body-system categories of codes include codes for nonspecific conditions. For example, the code for a breast lump is found in Volume I under “Genitourinary System,” in the subcategory “Signs and symptoms in breast,” and would be properly coded as 611.72, “Lump or mass in breast.” Use these codes (rather than codes for more specific disorders) when the only facts you have are the patient's signs and symptoms.

Coding several symptoms or diagnoses

When you need to list more than one diagnosis for your patient, prioritize them: Code the primary diagnosis first followed by the next most important and so on. The primary diagnosis should be the one that receives the most attention during the patient visit. For example, if a patient you're treating for hypertension presents with an upper respiratory infection, the infection would be considered the primary reason for the visit and should be listed first, followed by hypertension.

Patients with multiple diagnoses can pose quite a challenge (again, see “ICD-9 coding challenges” for an example). For example, you're treating a patient with poorly controlled diabetes, hypertension and coronary artery disease. Because you see the patient most often for blood-glucose monitoring, the primary diagnosis would be diabetes followed by hypertension and coronary artery disease (unless the patient had active signs or symptoms related to one of the other conditions). And here's a related tip: Don't code a diagnosis that doesn't affect your care of the patient. For example, if your patient with diabetes is also being treated by an orthopedist for a broken arm, don't code the fracture since it doesn't affect the care you're providing.

You may submit up to four diagnoses on a HCFA-1500 form, and (as noted above) you may link up to four diagnosis codes to each CPT code. But remember that some payers will read only the first ICD-9 code linked to the CPT code, so it's important to prioritize and link the ICD-9 codes accurately.

ICD-9 coding challenges

Evaluate your coding skills by choosing the correct ICD-9 code(s) for the following two patient visits. The answers and explanations appear below.

Case 1

A patient complains of epigastric pain. You suspect reflux esophagitis and order an upper GI series. What ICD-9 code(s) would you submit for this visit?

Case 2

A female patient complains of dysuria and increased frequency. A microscopic exam performed in your office reveals the presence of bacteriuria, and you order a culture. During the visit, the patient also asks you for a refill of Synthroid. Reviewing her medical history, you notice that she has not had her thyroid level checked in some time, and you perform a thyroid-stimulating hormone test. Assuming that this patient has Graves' disease, what ICD-9 code(s) would you submit for this visit?

Check your answers

For case 1, the correct code is 789.06 for “Abdominal pain, epigastric.” Although you may suspect reflux esophagitis (530.11), you can't make a definitive diagnosis until you receive the test results. Therefore, you must code only the symptoms. (Remember: Code only what you know.) Since proper coding requires use of the highest number of digits that best describe your patient's condition, you must use five digits here. The fifth digit describes the location of the pain. Avoid using a “default” fifth digit such as “0” to describe an unspecified site as it may cause some third-party payers to question the medical necessity.

For case 2, the answer is less straightforward; this visit may be coded several ways. You could choose code 788.1 for the dysuria and code 788.41 for the frequency. These symptoms would support the need for the office visit, microscopic exam and the subsequent culture. Since bacteriuria was present on examination, a definitive diagnosis (cystitis) was actually made at the time of the patient visit. Consequently, the visit and the tests could also be correctly coded as 595.0 (acute cystitis).

According to instructions in ICD-9-CM, the organism should also be coded; however, since you don't have the results of the culture, you can't yet identify the specific organism involved. Hence, 595.0 would be acceptable to most insurers. One could argue that this code shouldn't be used to support the microscopic exam because the symptoms, not the diagnosis, were the reason for performing it.

Next, you'll need to code the hyperthyroidism. The correct category is 242, “Thyrotoxicosis with or without goiter.” There are several choices under this heading. But since the patient has Graves' disease, the code 242.00 (“Toxic diffuse goiter without mention of thyrotoxic crisis or storm”) most accurately describes the patient's condition.

Finally, you must properly link the ICD-9 codes to each of the services provided. The primary reason for the visit is the dysuria and frequency. List these codes first, and link them to CPT codes for the two tests for the urinary complaints. The hyperthyroidism code should not be linked to the urinary tests. Link code 242.00 only to the thyroid-stimulating hormone test.

Who should do the coding?

No matter who actually does the coding in your practice, the physicians are legally responsible for the codes selected and submitted to payers. Since it's usually the physicians who have first-hand knowledge of what occurred during the patient visit, the initial code selection should come from them. Office staff can provide valuable help with the nuances of coding and specific payer requirements. Working as a team, physicians and staff can ensure that coding is done properly.

Why should I care?

Coding will never be the part of your work that you enjoy most; if it were, you wouldn't have bothered with medical school. But you do need to know the basics and be able to speak the language of coding. Why? The bottom line is your bottom line: Accurate coding of diagnoses, signs and symptoms helps to streamline payment from third-party payers. Although the coding system may seem confusing at first, it becomes an important management tool — once you get used to it.

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Copyright © 1999 by the American Academy of Family Physicians.

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