T32.42
BillableCorrosions involving 40-49% of body surface with 20-29% third degree corrosion
Last updated: FY2026 ICD-10-CM (Oct 1, 2025 – Sep 30, 2026) | CMS-HCC V28 (100% phase-in, PY2026)
Is T32.42 an HCC code?
Yes. T32.42 maps to Severe Skin Burn or Condition under the CMS-HCC V28 risk adjustment model (and Severe Skin Burn or Condition 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 T32.42
For T32.42 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 T32.42 during that encounter — not just copy-forwarded from a problem list.
What This Code Means
T32.42 is the ICD-10-CM diagnosis code for corrosions involving 40-49% of body surface with 20-29% third degree corrosion. Chemical burn affecting 40-49% of the body surface, with the most severe burns (third degree) covering 20-29% of the affected area. T32.42 sits in the ICD-10-CM chapter for injury, poisoning and certain other consequences of external causes (s00-t88), within the section covering burns and corrosions of multiple and unspecified body regions (t30-t32).
Under the CMS-HCC V28 risk adjustment model, T32.42 maps to Severe Skin Burn or Condition (HCC 385) with a community, non-dual, aged base RAF weight of 0.350. Under the older V24 model, T32.42 mapped to the same category but with a base RAF weight of 0.517 — V28 recalibrated weights across the entire model. 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.
Ensure the third-degree percentage is documented separately from the total body surface area involved. Because T32.42 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 T32.42 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Ensure the third-degree percentage is documented separately from the total body surface area involved
- •These codes indicate moderate to severe corrosion injuries requiring specialized burn center care
Clinical Significance
Corrosions involving 40-49% of body surface area with 20-29% third-degree involvement represent critical chemical burn injury with extremely high mortality risk requiring immediate life-saving interventions. This extensive chemical exposure pattern involves significant full-thickness tissue destruction alongside potential systemic toxicity, demanding specialized chemical burn center care with comprehensive toxicological support and intensive surgical intervention.
Documentation Requirements
- ✓Documentation of 40-49% total body surface area chemical corrosion
- ✓Clear documentation that 20-29% of affected area has third-degree corrosion
- ✓Identification of causative chemical agent and exposure details
- ✓Comprehensive emergency decontamination and neutralization documentation
- ✓Assessment of ongoing chemical activity and progressive tissue damage
- ✓Evidence of immediate chemical burn center admission
- ✓Documentation of systemic toxicity monitoring and specific antidotal therapy
- ✓Surgical planning for extensive debridement and reconstruction
Commonly Confused Codes
- •T31.42 — Thermal burns 40-49% TBSA with 20-29% third degree (thermal, not chemical)
- •T32.41 — Corrosions 40-49% TBSA with 10-19% third degree (less third-degree)
- •T32.43 — Corrosions 40-49% TBSA with 30-39% third degree (more third-degree)
- •T32.32 — Corrosions 30-39% TBSA with 20-29% third degree (smaller total area)
- •T32.52 — Corrosions 50-59% TBSA with 20-29% third degree (larger total area)