A40.0
BillableSepsis due to streptococcus, group A
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is A40.0 an HCC code?
Yes. A40.0 maps to Septicemia, Sepsis, Systemic Inflammatory Response Syndrome/Shock under the CMS-HCC V28 risk adjustment model (and Septicemia, Sepsis, Systemic Inflammatory Response Syndrome/Shock under V24).
HCC Category Mapping
RAF weights shown are the community, non-dual, aged base weights from the CMS risk adjustment model file. Actual per-patient RAF contribution depends on member segment, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains in use during the transition and for historical data.
MEAT Criteria for A40.0
For A40.0 to count as a valid HCC diagnosis in a given encounter, the provider's documentation must show MEAT: Monitor, Evaluate, Assess, or Treat. A diagnosis from a prior year does not carry forward automatically — it has to be re-documented and supported each calendar year.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Only one of M/E/A/T is required to support the code, but the documentation must be specific enough to show that the provider actually addressed A40.0 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
A40.0 is the ICD-10-CM diagnosis code for sepsis due to streptococcus, group a. A serious bloodstream infection caused by Group A Streptococcus bacteria that can spread throughout the body and cause organ failure. This is a life-threatening condition requiring immediate medical treatment. A40.0 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering other bacterial diseases (a30-a49).
Under the CMS-HCC V28 risk adjustment model, A40.0 maps to Septicemia, Sepsis, Systemic Inflammatory Response Syndrome/Shock (HCC 2) with a community, non-dual, aged base RAF weight of 0.455. The V24 model used during the PY2024–PY2025 transition mapped A40.0 the same way and at the same RAF weight. V28 is the CMS-HCC risk adjustment model that reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition.
Always verify the organism identification (Group A Streptococcus) is documented in the medical record before assigning this code. Because A40.0 maps to a payment HCC, the provider's documentation must satisfy MEAT criteria (Monitor, Evaluate, Assess, or Treat) for the encounter to count toward the patient's Medicare Advantage risk adjustment score. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for A40.0 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Always verify the organism identification (Group A Streptococcus) is documented in the medical record before assigning this code
- •Remember that sepsis codes require a secondary code for the associated organ dysfunction (SIRS criteria) and may require additional codes for the source of infection if documented
Clinical Significance
Sepsis due to Group A Streptococcus (Streptococcus pyogenes) is an aggressive, rapidly progressive bloodstream infection associated with necrotizing fasciitis, streptococcal toxic shock syndrome, and high mortality. Group A Streptococcal sepsis requires urgent source control, high-dose penicillin, and often clindamycin for toxin suppression.
Documentation Requirements
- ✓Blood cultures positive for Group A Streptococcus (S. pyogenes) or clinical sepsis with identified GAS source
- ✓Sepsis criteria met: documented infection with systemic inflammatory response
- ✓Source of infection identified (pharyngitis, cellulitis, necrotizing fasciitis, puerperal infection)
- ✓Severity indicators: organ dysfunction, hemodynamic status, vasopressor requirements
- ✓Complications documented: necrotizing fasciitis, streptococcal toxic shock syndrome, if present
Commonly Confused Codes
- •A40.1 (Sepsis due to Streptococcus, group B) — Group B Strep typically affects neonates and peripartum women; Group A causes pharyngitis-related and skin/soft tissue sepsis
- •A40.9 (Streptococcal sepsis, unspecified) — Use A40.0 when Group A is specifically identified; do not default to unspecified
- •A41.9 (Sepsis, unspecified organism) — Use A40.0 when Strep Group A is the identified organism