Asthma: Key coding considerations

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You need to be specific in your ICD-9 coding for asthma because there are several codes available.

Asthma is defined in the ICD-9-CM Expert for Physicians-Volumes 1 & 2 as “status asthmaticus: severe, intractable episode of asthma unresponsive to normal therapeutic measures.” You need to be specific in your ICD-9 coding for asthma because there are several codes available. If the documentation indicates that the asthma is both exacerbation and status asthmaticus, assign only the code for status asthmaticus.

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The main asthma category (493) requires a fourth and fifth digit, as shown in the table below. To code asthma, use the following steps:

Identify the asthma’s source with a fourth digit. The fourth digit identifies what caused the patient’s asthma. CPT contains four options for the fourth asthma digit:

  • 493.0x Extrinsic asthma

  • 493.1x Intrinsic asthma

  • 493.2x Chronic obstructive asthma

  • 493.9x Asthma, unspecified

Use a fifth digit to describe the asthma’s status. To identify the asthma’s current state during the patient’s visit, assign the appropriate fifth-digit subclassification.

  • 0 without mention of status asthmaticus or acute exacerbation or unspecified

  • 1 with status asthmaticus

  • 2 with acute exacerbation

For patients who do not have status asthmaticus or acute exacerbation, use the fifth digit of “0.” Code 493.x0 is appropriate when the patient presents for a checkup and his or her asthma is controlled.

The fifth-digit “1” indicates that the patient has status asthmaticus, which is a medical emergency and usually treated in the emergency department.

Assign a fifth-digit “2” for patients who present with asthma that is currently exacerbated. This means something made the patient’s asthma worse.

Paint an accurate picture with both digits. ICD-9 instructs coders to “assign fifth-digit subclassification codes for those categories where they are available.” The fourth and fifth digits are important because they paint a more complete picture of the patient’s condition at the time of the encounter. Without a complete picture, the payer may deny the claim for lack of medical necessity.

Because there are overlapping conditions between COPD and asthma, there are variations in documenting these conditions. Look to subcategory 491.2 if the patient has obstructive chronic bronchitis or category 492 for emphysema.


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