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A41.01

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codeA41.01
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🎗️ICD-10 CM A41.01 — Sepsis due to MSSA

Clinical Definition

ICD-10 CM A41.01 represents sepsis caused by Methicillin‑Susceptible Staphylococcus aureus (MSSA). This diagnosis requires clinical evidence of life‑threatening organ dysfunction resulting from a dysregulated host response to MSSA infection. MSSA is a common cause of bacteremia, pneumonia, endocarditis, and skin/soft‑tissue infections that may progress to systemic sepsis.

Documentation must clearly support:

  • Identified or strongly suspected MSSA as the causative organism
  • Clinical criteria for sepsis (infection + organ dysfunction)
  • Supporting labs such as positive blood cultures, elevated lactate, leukocytosis/leukopenia, or organ failure indicators

Coding Guidance

Key Coding Rules

  • Use A41.01 when MSSA is the confirmed or presumed cause of sepsis.
  • If the provider documents “sepsis due to staph aureus” and specifies MSSA, assign A41.01.
  • If MRSA is documented, use A41.02 instead.
  • If severe sepsis is present, add R65.20 or R65.21 as appropriate.
  • If septic shock is present, add R65.21 and sequence A41.01 first.

Sequencing

  • Principal diagnosis: A41.01 when sepsis is the reason for admission.
  • Secondary diagnosis: When sepsis develops after admission or is not the primary reason for encounter.

Includes / Excludes

Includes

  • Sepsis due to MSSA
  • Staphylococcus aureus septicemia when MSSA is specified

Excludes

  • MRSA sepsis — A41.02
  • Sepsis due to unspecified staphylococcus — A41.2

Use additional codes

Code Tree

A41 Sepsis
├── A41.0 Sepsis due to Staphylococcus aureus
│     ├── A41.01 Sepsis due to MSSA
│     └── A41.02 Sepsis due to MRSA
├── A41.1 Sepsis due to other specified staphylococcus
├── A41.2 Sepsis due to unspecified staphylococcus
├── A41.3 Sepsis due to Hemophilus influenzae
├── A41.4 Sepsis due to anaerobes
├── A41.5 Sepsis due to other Gram-negative organisms
├── A41.8 Other specified sepsis
└── A41.9 Sepsis, unspecified organism

MS‑DRG Impact

A41.01 is a major driver of DRGs 870-872, depending on mechanical ventilation and MCC/CC status.

  • DRG 870 — Septicemia/Severe Sepsis with MV >96 hours; Peripheral Extracorporeal Membrane Oxygenation (ECMO), even without mechanical ventilation
  • DRG 871 — Septicemia/Severe Sepsis without MV >96 hours with MCC
  • DRG 872 — Septicemia/Severe Sepsis without MV >96 hours without MCC

Sepsis codes frequently increase case weight due to high resource utilization.

HCC Impact

  • HCC 2 — Septicemia, Sepsis, Systemic Inflammatory Response Syndrome/Shock
  • High‑risk category with significant impact on risk adjustment models.
  • Requires clear provider documentation of sepsis criteria and causative organism.

Documentation Requirements

To support A41.01, documentation should include:

  • MSSA identified or clinically suspected
  • Evidence of systemic infection
  • Organ dysfunction attributable to infection
  • Source of infection when known (e.g., pneumonia, cellulitis, endocarditis)
  • Clinical indicators: lactate, WBC abnormalities, hypotension, organ failure
  • Treatment: IV antibiotics, fluids, vasopressors, ICU care

Coding Examples

Example 1

Documentation: “Patient admitted with sepsis due to MSSA bacteremia. Acute kidney injury present.”

Codes:

  • A41.01 — Sepsis due to MSSA
  • R65.20 — Severe sepsis (if documented)
  • N17.9 — Acute kidney injury

Example 2

Documentation: “MSSA pneumonia with sepsis. No shock.”

Codes:

  • A41.01 — Sepsis due to MSSA
  • J15.211 — Pneumonia due to MSSA
  • Add R65.20 if severe sepsis is documented

Example 3

Documentation: “Septic shock due to MSSA cellulitis.”

Codes:

  • A41.01 — Sepsis due to MSSA
  • R65.21 — Severe sepsis with septic shock
  • L03.90 — Cellulitis
  • A41.02 — Sepsis due to MRSA
  • A41.2 — Sepsis due to unspecified staphylococcus
  • R65.20 — Severe sepsis without shock
  • R65.21 — Severe sepsis with septic shock
  • J15.211 — MSSA pneumonia
  • B95.61 — MSSA as cause of diseases classified elsewhere

Notes for Auditors & Coders

  • Confirm MSSA vs MRSA — this changes the code.
  • Ensure sepsis criteria are met; avoid coding based solely on positive cultures.
  • Query when documentation is unclear regarding organism or sepsis severity.
  • Validate sequencing rules based on reason for admission.

Sources

CDC ICD‑10‑CM guidelines CMS MS‑DRG definitions manual AMA risk adjustment references

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