Healthcare Provider Solutions

Clinical Groupings – Primary Diagnosis


With the PDGM Final Rule CMS posted a complete list of ICD–10–CM codes and their assigned clinical groupings.

  • Based on the primary diagnosis, each 30-day period is placed into one of the 12 clinical groupings – HHAs should be familiar with codes that are used to group 30- day periods of care into the 12 clinical groupings.
  • If the primary diagnosis does not fit into one of the 12 clinical groups in the payment model, this is considered a “Unacceptable Diagnosis”.
  • Some additional notes are:
      • CMS states that the ICD–10–CM code list is an exhaustive list that contains many codes that do not support the need for home health services and so are not appropriate as principal diagnosis codes for grouping home health periods into clinical groups.
  • Under PDGM, if a claim is submitted by an agency with a primary diagnosis that does not fit into one of the 12 clinical groupings, the claim will be sent back to the agency as an RTP-Return to Provider. The agency will then need to review and resubmit the claim with a more appropriate primary diagnosis which does fit into a clinical grouping.
      • Furthermore, it is required per §409.43(c)(4) that any changes in the plan of care must be signed and dated by a physician. If a claim is returned for more specific coding, then it is expected that the diagnosis on the plan of care will be corrected with a signed order.


Comorbidities in PDGM


  • Coding is critical as two of the five categories for a PDGM HIPPS code results from diagnoses in the primary and secondary spots. PDGM includes comorbidities, which are defined as medical conditions coexisting with a principal diagnosis. They are tied to poorer health outcomes, more complex medical needs management and a higher level of care.
  • The premise is that by having the presence of home-health specific comorbidities as part of the overall case-mix adjustment, the reimbursement will account for differences in resource use based on patient characteristics. 3 comorbidity adjustment levels
  • No comorbidity adjustment: No secondary diagnoses exist or none meet the criteria for a low or high comorbidity adjustment.
  • Low comorbidity adjustment: There is a secondary diagnosis on the home health specific comorbidity subgroup list that is associated with higher resource use.
  • High comorbidity adjustment: Two or more secondary diagnoses on the home health specific comorbidity subgroup interaction list that are associated with higher resource use when both are reported together compared to if they were reported separately. The two diagnoses may interact with one another, resulting in higher resource use.
  • One comorbidity adjustment is permitted per 30- day period regardless of the number of secondary diagnoses or high comorbidity subgroup interactions reported on the claim. The highest level will be assigned.


Comorbidity Subgroups


  • There are 14 subgroups that can receive a low comorbidity adjustment
  • There are 31 High Comorbidity Adjustment Interaction Subgroups, however, 20 of the subgroups have interactions with either a non-pressure chronic ulcer or with a pressure ulcer. This includes diseases of arteries, arterioles and capillaries with ulceration and non-pressure, chronic ulcers or a pressure ulcer which includes stages two through four and unstageable pressure ulcers. Therefore, in only 11 of the interaction subgroups for a high comorbidity adjustment can the patient be without a non-pressure ulcer or a pressure ulcer.

Diagnoses Sequencing


  • Sequencing of the diagnoses, knowing which is primary and which are secondary, can be complex. Coding Guidelines from the ICD-10-CM Official Guidelines for Coding and Reporting should always be followed. That can mean that a diagnosis which is the primary reason for home health and documented by the physician on the face-to-face encounter could actually be in the first secondary diagnosis, rather than the primary, due to such rules as manifestation/ etiology codes or “code first” coding instructions. The primary service, highest frequency of discipline, etc. must be taken into account when assigning a primary diagnosis. Considering all of these factors, there can be variations in the diagnoses sequencing.
  • In addition to coding guidelines, the 2020 PPS final rule, the OASIS, and the CoPs give instructions for comorbidity coding that are not exactly the same, leading to confusion for agencies and coders alike. The ICD–10–CM Coding Guidelines define “other” (additional) diagnoses as “all conditions that coexist at the time of admission, that develop subsequently or that affect the treatment received and/or the length of stay.”  The OASIS D-1 Guidance Manual instructions state that “secondary diagnoses are comorbid conditions that exist at the time of the assessment, that are actively addressed in the patient’s plan of care or that have the potential to affect the patient’s responsiveness to treatment and rehabilitative prognosis.”  The CoPs at §484.60 state that the home health plan of care must include all “pertinent diagnoses’’ and the accompanying interpretive guidelines state that this means that all ‘‘known diagnoses.”
  • There are differences between the various descriptions, however, in the 2020 PPS final rule CMS stated that these instructions essentially describe the same thing:
      • “All of these coding instructions state to include any conditions that exist at the time of home health admission or that develop during the course of a home health period of care and that affect patient care planning.”
      • “Diagnoses should be reported that affect or potentially affect patient care(and therefore would be addressed in the home health plan of care), even if such care includes observation and assessment (for actual or potential effects), teaching and training or direct patient care interventions.”
      • Therefore, comorbidity/secondary diagnosis coding often will include diagnoses that affect or potentially affect patient care and those that will be addressed in the home health plan of care.


  • In order to capture correct comorbidity adjustments, you can see how important it is to receive all of the clinical history from the referral source, confirm the diagnoses with the physician, and code per coding guidelines.


Don’t miss our Alliance Members only webinar on 2021 Coding Updates For Home Health and Hospice.

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