2026 ICD-10-CM Diagnosis Code B44.0Invasive pulmonary aspergillosis
ICD-10-CM Codes›A00–B99›B35-B49›B44
- Billable — Valid for Submission
- MCC — Major Complication or Comorbidity
- Risk Adjusts — HCC 6
- Not Chronic
B44.0 is a billable ICD-10-CM diagnosis code for invasive pulmonary aspergillosis. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 177 through 179. As a secondary diagnosis, it counts as a major complication or comorbidity (MCC) and places an inpatient stay in the highest severity level of its MS-DRG family. It does not count, however, when the principal diagnosis is one of 129 closely related codes. Coders also document this condition as invasive aspergillosis. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Fungal infections and Other specified and unspecified lower respiratory disease.
For Medicare Advantage risk adjustment, B44.0 maps to CMS-HCC Category 6 (Opportunistic Infections) under the V28 model, adding a risk factor of about 0.381 for a community, non-dual, aged beneficiary in payment year 2026.
Code Identity
Code Classification
Medicare Risk Adjustment (HCC)Billing
B44.0 maps to a payment category in the CMS-HCC model used to risk-adjust Medicare Advantage payments. Weights are the published community factors for payment year 2026.
Source: CMS Payment Year 2026 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.
Approximate SynonymsGuidance
Alternate terms and clinical phrases that map to this code.
- Invasive aspergillosis
- Invasive pulmonary aspergillosis
- Pulmonary aspergillosis
- Subacute invasive pulmonary aspergillosis
Index to Diseases and InjuriesGuidance
Alphabetical index entries that point to this code.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Clinical InformationClinical
Invasive Pulmonary Aspergillosis
lung infections with the invasive forms of aspergillus, usually after surgery, transplantation, prolonged neutropenia or treatment with high-doses of corticosteroids. invasive pulmonary aspergillosis can progress to chronic necrotizing pulmonary aspergillosis or hematogenous spread to other organs.Pulmonary Aspergillosis
infections of the respiratory tract with fungi of the genus aspergillus.Aspergillus
a genus of mitosporic fungi containing about 100 species and eleven different teleomorphs in the family trichocomaceae.
Patient EducationClinical
Aspergillosis
Aspergillosis is a disease caused by a fungus (or mold) called Aspergillus. The fungus is very common in both indoors and outdoors. Most people breathe in the spores of the fungus every day without being affected. But some people get the disease. It usually occurs in people with lung diseases or weakened immune systems.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert B44.0 to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About B44.0Overview
What is the ICD-10 code for invasive pulmonary aspergillosis?
The ICD-10-CM code for invasive pulmonary aspergillosis is B44.0 (sometimes written as B440). It is billable on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
Is B44.0 (Aspergillosis) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report invasive pulmonary aspergillosis on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What MS-DRG does B44.0 group to?
When invasive pulmonary aspergillosis is the principal diagnosis on an inpatient stay, it groups to MS-DRG 177, 178, 179, with relative weights from 0.7550 to 1.5627 depending on complications. Higher weights mean higher Medicare reimbursement.
Is B44.0 a CC or MCC?
CMS lists B44.0 as an MCC (major complication or comorbidity) for FY 2026. Reported as a secondary diagnosis, it places the inpatient stay in the highest-weighted DRG of its severity family. It does not count when the principal diagnosis is one of the 129 closely related codes in its exclusion list.
What is the ICD-9 equivalent of B44.0?
Under the General Equivalence Mappings, invasive pulmonary aspergillosis converts to ICD-9-CM 117.3 (aspergillosis) and 484.6 (pneum in aspergillosis). The mapping is approximate, so confirm the match fits the documentation.
What HCC is B44.0?
B44.0 (invasive pulmonary aspergillosis) maps to CMS-HCC Category 6 (Opportunistic Infections), commonly written as HCC 6, in the CMS-HCC V28 model used for Medicare Advantage risk adjustment in payment year 2026. It mapped to HCC 6 under the retired V24 model. It also maps in the PACE (CMS-HCC V22), ESRD (V21), and ESRD (V24) models. In the Part D prescription drug model it maps to RxHCC 5.
Does B44.0 risk-adjust for Medicare Advantage payment?
Yes. When documented and reported on a Medicare Advantage encounter, B44.0 adds a risk adjustment factor of about 0.381 to the beneficiary's RAF score for a community, non-dual, aged enrollee (published V28 weights range from 0.381 to 0.833 depending on the payment segment). HCC 6 sits at the top of its hierarchy, so no other condition category supersedes it. See the full factor table on the HCC 6 category page.
