Question 1

What is ICD-10 code A55?

Accepted Answer

A55 is the ICD-10-CM diagnosis code for chlamydial lymphogranuloma (venereum). A sexually transmitted bacterial infection caused by chlamydia that causes painful swelling of lymph nodes, typically in the groin area. A55 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).

A55 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.

Confirm the diagnosis specifies lymphogranuloma venereum (LGV) caused by Chlamydia trachomatis L1-L3 serovars.

Question 2

Is A55 an HCC code?

Accepted Answer

No. A55 is a billable ICD-10-CM code but does not map to any payment HCC category under the CMS-HCC V28, V24, ESRD, or RxHCC risk adjustment models. It can still be reported on Medicare Advantage encounter data submissions, but it does not contribute to the beneficiary's Risk Adjustment Factor (RAF) score and therefore does not affect the risk-adjusted capitation payment to the plan. V28 reached 100% phase-in for payment year 2026.

Question 3

Is A55 billable?

Accepted Answer

Yes. A55 is a billable ICD-10-CM code that can be reported on professional and institutional claims as a primary or secondary diagnosis when the provider documentation supports the specific condition described. Billable codes in ICD-10-CM are coded to the highest level of specificity available for the documented diagnosis. A55 is current for fiscal year 2026 and remains in the active CMS ICD-10-CM code set published by the National Center for Health Statistics.

Question 4

What is the V28 vs V24 difference for A55?

Accepted Answer

A55 does not map to a payment HCC under either the CMS-HCC V28 risk adjustment model or the older V24 model. V28 reached 100% phase-in for payment year 2026, replacing V24 which was used during the PY2024–PY2025 transition. Because neither model rewards A55 with a risk adjustment factor, it contributes zero to a Medicare Advantage beneficiary's RAF score in either version. Coders should check whether provider documentation supports a more specific child code that does map to a payment HCC.

Question 5

What should coders know when reporting A55?

Accepted Answer

Confirm the diagnosis specifies lymphogranuloma venereum (LGV) caused by Chlamydia trachomatis L1-L3 serovars Document the stage of disease if applicable, as this may affect treatment decisions

A55

Is A55 an HCC code?

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Open A55 in the Interactive Encoder