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March 15, 2010

Coding for H1N1 Flu
For The Record
Vol. 22 No. 5 P. 28

H1N1 flu is a respiratory infection caused by an influenza virus. First recognized in April 2009, it became a global pandemic two months later.

H1N1 flu has been nicknamed swine flu because the virus that causes the disease came from pigs. (But the virus contains genes from swine, bird, and human flu viruses.) However, this type of flu is spread only from person to person, not from pigs or related products such as pork. Other names for H1N1 flu include novel H1N1 flu, nH1N1, 2009 H1N1 type A influenza, and H1N1 swine flu virus.

Children and young adults are most commonly diagnosed with H1N1 flu, but there is a vaccine available. The seasonal flu vaccine is not effective in treating H1N1 flu, but a patient can receive both types of flu vaccinations at the same time.

The symptoms most commonly associated with H1N1 flu include fever, cough, sore throat, runny nose, body aches, headache, chills, fatigue, diarrhea, and vomiting. Except for diarrhea and vomiting, these symptoms are similar to those of seasonal flu.

H1N1 flu develops three to five days after someone is exposed to the virus and lasts for eight days. The virus enters the body when someone inhales contaminated droplets or transfers a live virus from a contaminated surface to their eyes, nose, or mouth.

Potential complications of H1N1 flu include worsening of chronic conditions, pneumonia, and respiratory failure. Patients who are morbidly obese are more likely to develop a complication.

In most cases, H1N1 flu is diagnosed from the presenting signs and symptoms, though a rapid flu test may be performed to confirm the diagnosis. However, the test may give a negative result even if the virus is present. The lab test is performed only on those with severe flu symptoms.

The treatment focus is on the symptoms. Most H1N1 flu cases can be treated at home with bed rest. Antiviral drugs can reduce the severity and length of symptoms. However, flu viruses may develop a resistance to them. Therefore, it is antiviral medications are advised only after someone develops symptoms. Common antiviral medications include oseltamivir (Tamiflu), zanamivir (Relenza), and Peramivir, an IV drug used only for hospitalized patients. These antiviral medications work best if taken within 48 hours of the appearance of the first symptoms.

If a patient has a chronic respiratory disease, the physician may prescribe more medications to decrease inflammation, open the airways, and help clear lung secretions.

ICD-9-CM Coding Information
H1N1 flu is assigned to ICD-9-CM code 488.1, Influenza due to identified novel H1N1 influenza virus. According to current coding guidelines, only confirmed H1N1 flu cases are assigned to this code. A confirmed case does not require a positive laboratory finding, but it does require physician documentation that a patient has H1N1 flu (or swine flu). Do not assign 488.1 if the physician documents possible or probable H1N1. Instead, a code from category 487, Influenza, should be used.
Currently, there is no official published advice in Coding Clinic, nor does ICD-9-CM provide any clear direction regarding the appropriate code assignment and sequencing of H1N1 flu with pneumonia. Under category 487, there are several excludes notes that exclude influenza due to avian and H1N1 flu and directs the coder to category 488. Granted, the coder can code the specific type of pneumonia when a patient has influenza with pneumonia (487.0) due to coding directives under code 487.0. However, this same coding directive is not under category 488. Because coding directives require assigning the specific type of pneumonia with influenza unspecified, then it should be acceptable to assign a code for the precise type of pneumonia documented with a code for the avian or H1N1 flu (category 488). 

In addition, there are no sequencing guidelines on avian/H1N1 flu with pneumonia. It is 3M’s current recommendation that sequencing these two conditions depends on the circumstances of admission.

Since there is no published official advice on the coding and sequencing of H1N1 flu with pneumonia, the above recommendations are unofficial. Please refer to future issues of AHA Coding Clinic for ICD-9-CM for official advice.

Coding and sequencing for H1N1 flu are dependent upon the physician documentation in the medical record and application of the Official Coding Guidelines for inpatient care. Also, use specific AHA Coding Clinic for ICD-9-CM and American Medical Association CPT Assistant references to ensure complete and accurate coding.

— This information was prepared by Audrey Howard, RHIA, of 3M Consulting Services. 3M Consulting Services is a business of 3M Health Information Systems, a supplier of coding and classification systems to more than 4,000 healthcare providers. The company and its representatives do not assume any responsibility for reimbursement decisions or claims denials made by providers or payers as the result of the misuse of this coding information. More information about 3M Health Information Systems is available at www.3mhis.com or by calling 800-367-2447.