Section IV: Diagnostic Coding and Reporting Guidelines for Outpatient Services, deals with reporting diagnosis codes specifically in outpatient hospital and provider-based office settings. The guidelines in this section do not apply to inpatient services. The general guidelines from the other sections still apply, but there are a few variances you should always take note of.
One of the most important differences in inpatient and outpatient diagnostic coding, is the ability to use “likely” and “possible” diagnosis in the inpatient setting, unlike in outpatient coding. Instead, signs and symptoms are used when a definitive diagnosis is not available. New for 2020, the terms “consistent with” and “compatible with” have been added to describe uncertain diagnoses. You will not code diagnoses mentioned with these terms. When a patient presents for outpatient surgery, the first listed diagnosis should be the main reason for surgery. This should be obtained from the post-operative diagnosis, not the pre-operative diagnosis. If they develop complications from the surgery and require overnight (or longer) observation, the reason for the surgery still needs to be coded first, followed by the complication code(s).
As we discussed in previous blog posts, the first listed diagnosis should be the primary reason for the service on that day. Additional diagnoses can be used to describe other existing diagnoses. ICD-10 instructs us to code all documented conditions that coexist at the time of the visit and affected patient care. And be sure to NOT code conditions that were previously treated and no longer exist. History codes (categories Z80- Z87) may be used as secondary codes if the historical condition or family history has an impact on current care or influences treatment. Otherwise, it’s not necessary to add them.
What if a patient presents for diagnostic lab or x-ray services? Well, in these cases you will typically assign a code for the sign or symptom that prompted the test. For example, abdominal pain for a CT, or absence of menstruation for a pregnancy test. If the provider has access to the test results prior to submitting the claim, you should use the final diagnosis discovered as your first-listed diagnosis and NOT the signs or symptoms. If the provider reads the CT, and it shows appendicitis, the code for appendicitis should be used instead of abdominal pain.
For therapeutic services (such as IV hydration) you should code the condition that is listed by the provider as the primary reason for hydration. A provider may list nausea and vomiting as the reason, but also lists a condition that could cause N/V, perhaps pregnancy or cancer. You’ll need to refer to the coding guidelines for those chapters to ensure that you list the codes in the correct order.
The only exception to this rule is when a patient presents for chemotherapy or radiation therapy. In those cases, refer to the guidelines for Chapter 2 when reporting these therapies. And when in doubt, ask the provider.
Pre-operative (pre-op) evaluations are one of the more common diagnostic coding errors. The correct order to report pre-op evals is:
- Report a code from subcategory Z01.81 – Encounter for pre-procedural examinations
- Code the surgical diagnosis – The reason the patient is having surgery
- Optional – Code any conditions that are managed during the visit (hypertension, diabetes, etc.)
The last 2 bullet points in this section are the errors I see most often while auditing. These are the preventive medicine services, when the patient presents without a disease. In these cases, the appropriate code(s) from Chapter 21, Factors Influencing Health Status and Contact with Health Services, are used. What many providers and coders miss, is the fact that there are codes dealing with abnormal findings.
As per the AHA Coding Clinic (2016 Vol3 No1): “For the purpose of assigning codes from this category, an “abnormal finding” is a newly discovered condition, or a known/chronic condition that has increased in severity, (e.g., uncontrolled, and/or acutely exacerbated).” Often, code Z00.00, Encounter for general adult medical exam without abnormal findings gets submitted instead of Z00.01, Encounter for general adult medical exam with abnormal findings. The same concept applies to codes Z00.121, Encounter for routine child health exam with abnormal findings and code Z00.129, Encounter for routine child health exam without abnormal findings.
If a child presents to the pediatrician for his or her Well Child check, and is diagnosed with otitis media (OM), code Z00.121 is billed as the primary, along with the code for the OM. Always use the abnormal findings diagnosis if there is a new problem or an exacerbation of an existing one. It is not necessary to use it if there are chronic conditions listed that are stable.
In any case where the order of the diagnoses is not clear, always ask your provider. Remember: Correct coding = clean claims!