Guidelines for Determining the Appropriate Diagnosis Code

1. The allergist should become familiar with the ICD-10CM book. Even though most practices today have all diagnosis codes accessible in an electronic format, at least one copy of a book should be available. This allows for crosschecking and referencing when there is a question regarding the appropriate diagnosis code for a patient’s signs, symptoms or diseases. Even though most books are set up in the same format, each publisher has its own system. You should read the introduction for your specific book. It is important to understand when you need additional codes, what codes may be used only as secondary codes, and when you need additional information to have a complete code. This information is available in the general instructions, the chapter instructions or in the subsection instructions. If you rely completely on your diagnosis codes in your electronic practice management system or your electronic health record, you may not have the most accurate code for your patient encounters. Also, the direct translation of the code you are looking for has a good chance of being different from what you may have done in the past and may expect in ICD-10. If your system has been cross-walked from an ICD-9 coding system to an ICD-10 coding system, make sure you verify the accuracy of the codes. If a superbill is used as a communication tool within the practice, this tool also must be revised and updated with verification of the correct codes from the ICD- 10 CM diagnosis coding book.

2. Always use both the alphabetic and the tabular sections to select a diagnosis code. The alphabetical index will indicate with a √ after the code as an indication of the need for additional number(s) or letter(s) only provided in the Tabular section of the ICD-10CM book. In the Neoplasm Table, a – (dash) is added to indicate the need for additional information as well as the √ indicating an additional digit is needed. 

3. Always code the reason why the patient sought medical advice as the primary diagnosis. 

4. Do not code “probably,” “possible” or “rule-out” diagnoses. When the patient’s diagnosis is not definite, you should code signs and symptoms until the diagnosis is definite. The following coding guidelines in the ICD-10 CM book state: 

a. “Sign/symptom and “unspecified” codes have acceptable, even necessary, uses. While specific diagnosis codes should be reported when they are supported by the available medical record documentation and clinical knowledge of the patient’s health condition, there are instances when signs/symptoms or unspecified codes are the best choices for accurately reflecting the healthcare encounter. Each healthcare encounter should be coded to the level of certainty known for that encounter. 

b. If a definitive diagnosis has not been established by the end of the encounter, it is appropriate to report codes for sign(s) and or symptom(s) in lieu of a definitive diagnosis. When sufficient clinical information isn’t known or available about a particular health condition to assign a more specific code, it is acceptable to report the appropriate  “unspecified” code (e.g., a diagnosis of pneumonia has been determined, but not the specific type). Unspecified codes should not be reported when there are codes that more accurately reflect what is known about the patient’s condition at the time of that particular encounter. It would be inappropriate to select a specific code that is not supported by the medical record documentation or conduct medically unnecessary diagnostic testing in order to determine a more specific code.

5. Code the diagnosis to the highest degree of clinical certainty by using the highest level of code. Asthma, for example, has a two digit subsection-code, J45. Asthma is further divided into subsections with a third digit explanation as follows: 

a. mild intermittent (J45.2) 

b. mild persistent (J45.3) 

c. moderate persistent (J45.4) 

d. severe persistent (J45.5) 

e. unspecified asthma (J45.9)

 The fifth digit for asthma indicates:

 a. uncomplicated (0)

 b. with acute exacerbation (1)

 c. with status asthmaticus (2) Therefore, a patient who has mild persistent asthma with an acute exacerbation would be coded with the diagnosis code J45.31.

6. If there is a comorbidity which is considered in the clinical judgment of the allergist in caring for the patient and the documentation supports the clinical consideration of that, these conditions also need to be coded. These codes would be listed as secondary codes to the primary code the patient is being assessed for by the allergist. For example an asthmatic patient also has diabetes and the use of steroids for control and impacted by the diabetes.