Influenza in ICD10

We are aware that the instructions in this article are different from our old definition and from the tmp projects. Please do not use these instructions at this time. We will get back to them in January when everyone is back from vacation. In the meantime, please use the following instructions: 
* Influenza treated
* Influenza tracking

ICD10 Codes for Influenza

There are 4 influenza-related codes we're using in ICD10.

• 3 code are for actual disease due to influenza:
  • Influenza pneumonia
  • Influenza without pneumonia but with other respiratory manifestations
  • Influenza with nonrespiratory manifestations
• The 4th has a long & weird name: Influenza virus NOS -- should almost never be used (see more info in that article)
• Don't confuse influenza with either of: Haemophilus influenzae (H. flu) OR Parainfluenza virus
• See: Wikipedia for types of virus included

Identifying the Presence of Influenza

• It's not always simple. The reason is that the value of lab tests in helping us figure out whether a person has influenza depends on:
  • a) how long after onset of symptoms the test was done
  • b) which test was done,
  • c) whether the sample was upper or lower respiratory, and (d) when, relative to that year's flu season the test was done.

• Based on this, ICD-10 coding for identification of influenza will be as follows:
  • Look at this WRHA website https://www.gov.mb.ca/health/publichealth/surveillance/influenza/index.html to identify whether we’re in flu season
  • During flu season a person will be considered to have influenza if either of the following is true: (i) any lab test done for influenza was positive, or (ii) the patient was believed the the medical team to have influenza and given a full course of treatment (which could possibly have concluded after leaving the hospital, or they could have died before completing the full course).
    • NOTE that a person can be diagnosed as having influenza even if no test was sent, OR EVEN when tests sent were negative if they meet criterion "ii".
    • For (i) during flu season, "any lab test" means preliminary Cadham result or final Cadham result, or even the rapid swab done by the individual hospital labs.
  • Off flu season (before there is any reported flu in the province, and after the flu season has been declared to be over) a person can ONLY be diagnosed as having influenza if the FINAL CADHAM test result is positive. In the absence of such a final Cadham result, clinical suspicion, treatment for flu, and positive rapid tests will be considered as NOT INFLUENZA.
• The way this definition differs from that of the WRHA is primarily that -- if a test was done -- they consider a person negative (influenza ruled out) if the final Cadham result is negative, while during flu season we consider that person to be +influenza if the medical team thought they had influenza and gave the person a full course of treatment.
  • We are aware that neither of these approaches are THE TRUTH. The WRHA definition almost certainly slightly undercounts cases, while our ICD10 definition listed above almost certainly slightly overcounts cases.

• To satisfy the data demands of the Critical Care Program, we will continue to record whether:
  • [1] A lab test for influenza was done and whether it was positive or negative.
    • As of January 2018 there are 3 "flavors" of influenza tests being done in the WRHA. First some individual hospital labs run a test locally, done only on swabs (not body fluids). Second and third, Cadham does both a preliminary and final testing, which they will run on either swabs or body fluids.
      • During flu season we consider testing to be positive if ANY test done was reported as positive -- even if others were negative.
      • Off of flu season we consider testing to be positive only if the FINAL CADHAM result was positive. Thus, off of flu season influenza tests done by the separate hospital labs and preliminary Cadham results are ignored.
  • [2] Whether a “full course” of treatment was given for influenza, with oseltamivir (Tamiflu) or another anti-flu agent. A full course of Tamiflu is 5 days for mild disease. But WHO and CDC recommend that in severe cases (including all cases requiring mechanical ventilation) the drug should be continued until the infection is resolved or there is satisfactory clinical improvement.

Alternate ICD10s to consider coding instead or in addition

• Haemophilus influenzae (H. flu)
• Parainfluenza virus

Template:CCMDB Data Integrity Checks

None yet. Do we need any? Possibly with Template:Discussion

• Influenza virus
• Pharm influenza drugs
• Dxs
  • old: Tracheobronchitis
  • new (see above)

• caution about putting a cross check with influenza drugs, as there are times when a patient is given the med for suspect influenza however, the Cadham lab report comes back as negative.
  • Best to wait until we have some data to do this. Tina has scheduled review with Julie for 3rd week of November.

Possible checks:

• if there was a confirmed tmp entry, there has to be a dx
  • maybe no drug and if DC treat or comfort care?
• if there is a dx... can't do any cross checks in old dx because tracheobronchitis isn't always influenza, right? Might work with the new dxs, though, they are influenza specific
• if there is a drug... are they ever used for anything else? would coding for influenza go away if lab comes back clean? Might not be able to do anything with the drugs.