Updated on: September 23, 2013

Coding for Drug-Resistant Microorganisms in ICD-10-CM

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Original story posted on: February 6, 2012

There are a growing number of pathogenic microorganisms that are resistant to some or all of the drugs previously used to treat the infections they cause.

Until the 2012 ICD-10-CM draft version was released, drug-resistant infections were captured with a single code: Z16, Infection with drug-resistant microorganisms. Even Methicillin-resistant Staphylococcus Aureus (MRSA) infections did not have specific codes, as they do in ICD-9-CM. In the 2012 draft, combination codes have been added for MRSA infections and category Z16 has been expanded to include a number of supplementary codes for reporting infections caused by drug-resistant microorganisms.

Methicillin-susceptible and Methicillin-resistant Staphylococcus Aureus Infections

S. aureus is found on the skin and in the nasal cavities of 25-30 percent of the U.S. population. This is called "colonization," and healthy individuals with S. aureus colonization are called "carriers." In most healthy individuals, colonization causes no major problems. However, if the microorganisms get into the body through a cut or an open area, S. aureus can become a serious or even life-threatening infection. For coding purposes, S. Aureus is classified as Methicillin-susceptible, also called MSSA, or Methicillin-resistant, also called MRSA. (Codes are also available for other and unspecified staphylococcus infections.) MRSA is found on the skin of approximately 1-2 percent of healthy individuals, and this strain is resistant to most antibiotics commonly used to treat staph infections – making the infection much more serious and difficult to treat. Like other strains of staphylococcus, MRSA bacteria usually enter the body through a broken area in the skin, although other entry sites include the respiratory tract, surgical or other open wounds, intravenous catheters, and the urinary tract. While most MRSA infections involve only the skin and present as boils or small bump-like blemishes, serious and often life-threatening infections also can occur, causing conditions such as cellulitis, sepsis and pneumonia. Patients with compromised immune systems are at significantly greater risk of symptomatic secondary infection.

Coding guidelines for reporting S. aureus infections are as follows:

  • Combination codes:
    • ICD-10-CM – There are combination codes for MRSA sepsis (A41.02), MRSA pneumonia (J15.212), MSSA sepsis (A41.01) and MSSA pneumonia (J15.211). A code from subcategory Z16.11, Resistance to penicillins, is not reported additionally for MRSA sepsis or pneumonia because the combination code captures both the infectious organism and the drug-resistant status.
  • Unspecified site:
    • ICD-10-CM – MSSA infection of an unspecified site is reported with code A49.01. MRSA infection of an unspecified site is reported with code A49.02.
  • Other MRSA infections:
    • ICD-10-CM – Documentation of infection due to MRSA not covered by a combination code (such as a wound infection, stitch abscess or urinary tract infection) is reported with the code for the condition, followed by the code B95.62, Methicillin-resistant S. aureus (MRSA). This is done to indicate infection as the cause of diseases classified elsewhere and to identify the drug-resistant nature of the infection. A code from subcategory Z16.11, Resistance to penicillins, is not reported additionally.
  • MRSA or MSSA colonization:
    • ICD-10-CM – Documentation of MRSA or MSSA colonization without documentation of a disease process due to the MRSA or MSSA is reported with code Z22.322, Carrier or suspected carrier of MRSA, or Z22.321, Carrier or suspected carrier of MSSA. Positive tests might be documented as "MRSA screen positive" or "MSSA nasal swab positive." Documentation of MRSA or MSSA colonization with documentation of a current MRSA or MSSA infection requires reporting of both conditions, using both the code for the MRSA or MSSA infection and the code for the carrier state.

Coding for Other Drug Resistant Microorganisms

The code for the condition or infectious microorganism is reported first, followed by the code for the drug-resistant nature of the infection.

  • Condition/Microorganism:
    • ICD-10-CM – Again, the code that identifies the microorganism is listed first. For example, tuberculosis of the lung with resistance to isoniazid would be reported with code A15.0, Tuberculosis of lung, followed by the code that identifies the drug resistance.
  • Supplementary codes:
    • ICD-10-CM – Bacterial infections documented as drug-resistant or antibiotic-resistant.
      • For a current infection due to MRSA not covered by a combination code, (such as a wound infection, stitch abscess or urinary tract infection), again, use the code for the condition followed by the code B95.62, Methicillin-resistant S. aureus (MRSA) infection, as the cause of diseases classified elsewhere to identify the drug-resistant nature of the infection.
      • For all other drug-resistant microorganisms, use a code from category Z16. Using the example above for tuberculosis of the lung with resistance to isoniazid, the drug resistance would be reported with Z16.431, Resistance to single antimycobacterial drug.

About the Author

Lauri Gray, RHIT, CPC, is the clinical technical editor of coding and reimbursement print and electronic products for Contexo Media. She has worked in the health information management field for 30 years and began her career as a health records supervisor in a multi-specialty clinic. Following that she worked in the managed care industry as a contracting and coding specialist for a major HMO. Lauri has also taught medical coding at the College of Eastern Utah.  She is a member of the American Academy of Professional Coders (AAPC) and the American Health Information Management Association (AHIMA).

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