A51.5 ICD-10-CM Code: Early syphilis, latent
HCC Buddy Code Card
Digital ICD-10 code-book layout with official code detail, always-visible risk models, Code Trumping, and Buddy coding guidance.
FY 2026 Apr update / Certain infectious and parasitic diseases (A00-B99) / Infections with a predominantly sexual mode of transmission (A50-A64)
A51.5
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceEarly syphilis, latent
This is a stage of syphilis where a person has been infected with the syphilis bacteria but shows no visible symptoms or signs of the disease. The infection is present in the body and can be detected through blood tests, but the person appears and feels healthy.
CMS-HCC V28
00
RAF 0
CMS-HCC V24
00
RAF 0
ACA/HHS
00
RAF 0
ESRD/PACE
00
RAF 0
RXHCC
00
RAF 0
Code Trumping
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Code Book Path
Inclusion Terms
Official- Syphilis (acquired) without clinical manifestations, with positive serological reaction and negative spinal fluid test, less than two years after infection.
Excludes 2
OfficialICD-10-CM does not list Excludes 2 notes for A51.5 in this effective period.
Related Child Codes
Includes
OfficialICD-10-CM does not list Includes notes for A51.5 in this effective period.
Excludes 1
OfficialICD-10-CM does not list Excludes 1 notes for A51.5 in this effective period.
Code First
OfficialICD-10-CM does not list Code First sequencing instructions for A51.5 in this effective period.
Use Additional
OfficialICD-10-CM does not list Use Additional Code instructions for A51.5 in this effective period.
Code Also
OfficialICD-10-CM does not list Code Also instructions for A51.5 in this effective period.
Buddy Documentation Tip
Last updated: FY2026 ICD-10-CM Apr update, Apr 1, 2026 through Sep 30, 2026. CMS-HCC V28 is 100% phased in for payment year 2026.
Is A51.5 an HCC code?
No. A51.5 is a billable ICD-10-CM code but does not map to any HCC category in V28, V24, ESRD, or RxHCC.
Coder workflow notes
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This code does not map to an HCC category in any model (V28, V24, ESRD, RxHCC).
What This Code Means
A51.5 is the ICD-10-CM diagnosis code for early syphilis, latent. This is a stage of syphilis where a person has been infected with the syphilis bacteria but shows no visible symptoms or signs of the disease. The infection is present in the body and can be detected through blood tests, but the person appears and feels healthy. A51.5 sits in the ICD-10-CM chapter for certain infectious and parasitic diseases (a00-b99), within the section covering infections with a predominantly sexual mode of transmission (a50-a64).
A51.5 is a billable ICD-10-CM code but does not map to a payment HCC under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can be reported on Medicare Advantage encounter data submissions but it does not contribute to a beneficiary's RAF score and therefore does not affect risk-adjusted payments to the plan.
Ensure documentation clearly indicates the latent stage of early syphilis (typically within the first 2 years of infection) rather than late latent syphilis, as they have different codes.
HCC Buddy maintains structured V28 and V24 mapping, RAF weights, and MEAT documentation criteria for A51.5 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Ensure documentation clearly indicates the latent stage of early syphilis (typically within the first 2 years of infection) rather than late latent syphilis, as they have different codes
- •Verify that serological test results confirming syphilis infection are present in the medical record, as latent syphilis is diagnosed through blood tests rather than clinical symptoms