M05.A — Abnormal rheumatoid factor and anti-citrullinated protein antibody with rheumatoid arthritis

Billable

Is M05.A billable?

Yes — M05.A is billable for FY2027. M05.A is a valid, billable ICD-10-CM code at the highest level of specificity in its branch. M05.A may be submitted for encounters from October 1, 2026 through September 30, 2027.

M05.A at a glance

Code	M05.A
Description	Abnormal rheumatoid factor and anti-citrullinated protein antibody with rheumatoid arthritis
Billable	Yes
Code set	ICD-10-CM FY2027
Valid for encounters	October 1, 2026 – September 30, 2027

Which MS-DRGs does M05.A group to?

M05.A sits in MDC 08 and helps define the logic of 3 MS-DRGs (version 44, FY2027). Which one a stay actually groups to also depends on procedures and secondary diagnoses.

545Connective Tissue Disorders with MCCmedical
546Connective Tissue Disorders with CCmedical
547Connective Tissue Disorders without CC/MCCmedical

How is M05.A listed in the Alphabetic Index?

These are the routes through the Alphabetic Index that lead to M05.A. They show the wording a clinician may have documented, which often differs from the Tabular description.

Abnormal, abnormality, abnormalities › rheumatoid factor and anti-citrullinated protein antibody › with rheumatoid arthritis

Code first

The underlying condition below must be sequenced before M05.A. M05.A describes a manifestation and cannot be the principal or first-listed diagnosis.

rheumatoid arthritis with rheumatoid factor by site, if known (M05.00 to M05.8A)

Excludes1 — never code together — inherited from M05

The conditions below can never be reported together with M05.A on the same claim. An Excludes1 note means the two conditions cannot occur in the same patient, so reporting both is a coding error.

rheumatic fever (I00)
juvenile rheumatoid arthritis (M08.-)
rheumatoid arthritis of spine (M45.-)

Excludes2 — not included here — inherited from Chapter 13

The conditions below are not part of M05.A, but a patient may have both at the same time. When documentation supports it, M05.A and the excluded code may both be reported.

arthropathic psoriasis (L40.5-)
certain conditions originating in the perinatal period (P04-P96)
certain infectious and parasitic diseases (A00-B99)
compartment syndrome (traumatic) (T79.A-)
complications of pregnancy, childbirth and the puerperium (O00-O9A)
congenital malformations, deformations, and chromosomal abnormalities (Q00-Q99)
endocrine, nutritional and metabolic diseases (E00-E88)
injury, poisoning and certain other consequences of external causes (S00-T88)
neoplasms (C00-D49)
symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified (R00-R94)

How long has M05.A existed?

M05.A first appears in FY2026.

Derived from the official order files for FY2016–FY2026. FY2017 and FY2020 publish no order file, so those years are not covered.