Dermatology prior authorization and medical necessity documentation.
Biologics carry dermatology's densest prior-authorization burden, and unlike Medicare's LCD-driven coverage rules for Mohs or lesion removal, there's no federal coverage document to point to — each commercial payer sets its own BSA threshold, its own step-therapy list, and its own accepted severity tool for psoriasis, atopic dermatitis, and hidradenitis suppurativa. Layered on top of that is dermatology's other major medical-necessity problem: cosmetic reclassification, which is driven by what the note says, not which ICD-10 code is attached. This guide covers both — the biologic PA documentation payers actually require, and the exact language that separates a defensible medical-necessity note from a CO-50 denial.
Key takeaways
- There is no Medicare LCD governing biologic coverage for psoriasis, atopic dermatitis, or HS. This is commercial medical-policy and Part D formulary territory entirely — "per CMS guidance" isn't a valid citation for a biologic PA denial.
- "BCBS" isn't one payer. Each Blue Cross Blue Shield licensee is a separate legal entity with its own medical policy — the same trap as citing "the LCD" without naming the MAC, and it costs PA staff time when they pull the wrong plan's criteria.
- Cosmetic denials are a documentation-habit problem, not a coding problem. A technically correct ICD-10 code attached to a note that only describes appearance still reads as cosmetic to a claims reviewer.
- An ABN protects revenue on genuinely borderline cases — but only when it names the specific service and the specific coverage doubt, signed before the service, not requested after a CO-50 denial lands.
Why this isn't LCD territory
Dermatology's other coverage questions — Mohs, benign lesion removal — run through Medicare Administrative Contractor LCDs, which at least gives a practice a specific document to cite. Biologic coverage for psoriasis, atopic dermatitis, and hidradenitis suppurativa doesn't work that way: a direct search of the CMS Coverage Database against these conditions returns no active local coverage determination naming any of them. Coverage for these drugs runs through commercial payer medical policy and, for Medicare beneficiaries, Part D formulary and utilization-management criteria rather than a Part B LCD. That matters operationally because it means there's no single authoritative source to pull a threshold from — the payer's own current medical policy document is the only citation that holds up, and "per CMS guidance" or "per the LCD" is simply the wrong citation for a biologic PA denial in this specialty.
Biologic PA: the pattern across three conditions
Psoriasis, atopic dermatitis, and hidradenitis suppurativa biologics are gated by the same underlying structure even though the specific thresholds differ: a documented severity or extent measure, plus documented failure of at least one conventional therapy, before a biologic gets approved.
| Condition | Typical severity gate | Typical step-therapy requirement | Diagnosis specificity payers gate on |
|---|---|---|---|
| Moderate-to-severe plaque psoriasis | BSA in the 3–10% range, or a validated score (PASI, PGA) plus functional impact for lower BSA involving face/hands/feet/genitals ⚠️ | At least one failed conventional systemic (commonly methotrexate) and/or phototherapy, agent list varies by payer | L40.0 vulgaris rather than L40.9 unspecified; arthropathic involvement (L40.50) can change the approved drug class |
| Atopic dermatitis / eczema | Validated severity score (commonly EASI or IGA) plus documented inadequate response to topical therapy ⚠️ | Topical corticosteroids and/or calcineurin inhibitors trialed and failed or contraindicated; systemic agent trial required by some payers | Subtype code (L20.81–L20.84) rather than L20.9 unspecified, especially for payers that differentiate by clinical phenotype |
| Hidradenitis suppurativa | Hurley stage or a validated HS severity measure, documented at the affected sites ⚠️ | Documented failure of oral antibiotics and/or topical therapy; fewer approved conventional steps exist than for psoriasis, so requirements are often lighter | L73.2 hidradenitis suppurativa — already reasonably specific, but site and stage documentation still has to accompany it |
⚠️ The severity-gate percentages and score thresholds above reflect thresholds commonly cited in industry PA guidance and are not independently verified against a specific payer's current published medical policy during this build — automated retrieval of individual commercial payer policy pages was not reliable enough to confirm live figures for this page. Pull the specific payer's current medical policy document before submitting a PA rather than applying any threshold listed here.
Payer-by-payer variance is real, not a formality
Treating "the payer requires 10% BSA" as a universal rule is the same mistake as treating "the LCD says" as a universal Medicare citation — it's plan-specific, and naming the plan is what makes a PA submission or appeal actually work.
- 1"BCBS" is not one payer. Each Blue Cross Blue Shield licensee — Anthem, Highmark, Horizon, and dozens of others — is an independently operated company with its own medical policy library. A BSA threshold or step-therapy list pulled from one BCBS licensee's policy does not apply to a different licensee, even in a neighboring state.
- 2National payers (UnitedHealthcare, Aetna, Cigna, Humana) each publish and update their own biologic medical policy documents, typically through their specialty pharmacy or utilization-management division rather than the core medical policy library, and those documents are revised through the year independent of any annual code-set cycle. A policy pulled six months ago may already be superseded.
- 3Medicaid managed-care plans layer state-specific preferred drug lists on top of the underlying MCO's national criteria, so a biologic PA workflow built around commercial-payer logic often needs a separate branch for Medicaid MCO patients rather than a shared rule set.
The operational fix is the same one that works for MAC-specific LCDs: identify the plan on the claim first, pull that plan's specific current policy document, and don't let a remembered threshold from a different payer or an earlier policy version drive the submission.
The cosmetic-versus-medically-necessary documentation trap
This is dermatology's most common denial reason by industry reporting, and it isn't a coding problem — a technically accurate, specific ICD-10 code doesn't protect a claim if the note itself only describes how a lesion looks. Reviewers read the narrative, not just the code.
- Functional impairment — interferes with shaving, vision, hearing (ear lesions), or clothing/protective equipment fit
- Bleeding with minor trauma or friction from clothing
- Recurrent irritation, inflammation, or infection at the site
- Documented change in size, shape, color, or border (malignancy suspicion, ABCDE criteria)
- Pain or tenderness at the site, independent of appearance
- "Patient concerned about how it looks" with nothing further
- "Patient wants it removed" as the sole stated reason
- A diagnosis code entered with no supporting narrative in the note at all
- "For cosmetic improvement" or any variant, even when a medical reason exists but wasn't written down
The gap between those two columns is a documentation habit, not a clinical judgment call — in most cases, a genuine medical reason exists and simply isn't captured in the note. Templating the exam to prompt for symptom, function, or change at every lesion evaluation, not just the diagnosis field, is the single highest-leverage fix available, because it closes the gap before the claim is ever submitted rather than trying to win it back on appeal.
ABNs when medical necessity is genuinely borderline
- 1Use it before the service, not after the denial. An Advance Beneficiary Notice has to be signed by the Medicare patient before the procedure, naming the specific service and the specific reason coverage might be denied — a generic or routinely-signed ABN doesn't hold up on review.
- 2The clearest trigger cases: a lesion removal where the documentation could plausibly still read as borderline even after the note is improved, a repeat destruction without a clearly new or changed clinical finding, or any service the practice has specific reason to believe may not meet a particular LCD's coverage criteria for that diagnosis.
- 3ABNs are Medicare-specific. Commercial payers have their own financial-responsibility and waiver processes, which are separate documents with separate rules — an ABN signed for a Medicare patient doesn't transfer to a commercial plan's version of the same situation.
Keep a payer-specific PA criteria sheet updated per plan — not per payer brand — for every biologic your practice prescribes regularly. "UnitedHealthcare" and "the BCBS plan in our top ZIP codes" are two different sheets with two different step-therapy lists, and a shared generic sheet is exactly what produces PA denials on documentation that would have passed under the correct plan's actual criteria.
Once a biologic PA or a lesion-removal claim does deny, the CARC on the remit decides how it gets worked — missing-PA denials (CO-16/PR) and cosmetic reclassification (CO-50) require different follow-up entirely, covered with the full appeal-argument mapping in our dermatology billing modifiers guide and the pillar's denials section.
Biologic PAs and cosmetic denials eating staff time?
We'll audit a sample of your recent PA submissions and CO-50 denials, name the payer-specific gaps actually causing them, and show what's recoverable.
Frequently asked questions
What BSA threshold do payers require before approving a psoriasis biologic?
There's no single number — most payer medical policies for moderate-to-severe plaque psoriasis set a body surface area threshold somewhere in the 3-10% range, with 10% BSA commonly treated as close to automatic approval and lower BSA often qualifying instead on documented functional impact, especially when the face, hands, feet, or genitals are involved. The exact cutoff, the accepted severity tool (BSA, PASI, PGA), and which conventional systemic agents count as a completed step vary by payer and by plan, and each major payer maintains its own current policy rather than following a shared industry standard. Pull the specific payer's current criteria before submitting rather than applying a remembered threshold.
What documentation language protects a lesion removal claim from a cosmetic (CO-50) denial?
Payers reclassify a claim as cosmetic based on what the note says about why the procedure was done, not the ICD-10 code attached to it. Language that survives review names a functional or symptomatic reason: interferes with shaving, vision, or clothing; bleeds with minor trauma; recurrently irritated or infected; changing in size, shape, or color; or raises suspicion for malignancy. Language that reads as cosmetic and predicts a denial describes only appearance — "patient concerned about how it looks," "wants it removed," or a diagnosis code with no supporting narrative at all. The distinction lives in the note's own words, not in code selection.
When should we use an ABN for a dermatology procedure?
Use an Advance Beneficiary Notice whenever a Medicare patient's medical necessity is genuinely borderline going into the visit — a lesion that could plausibly read as cosmetic on review, a repeat destruction without a clearly changed clinical picture, or a service the practice has reason to believe may not meet a specific LCD's coverage criteria. The ABN has to be signed and on file before the service is performed, with the specific service and the specific reason coverage might be denied named on the form — a blanket or routinely-signed ABN doesn't hold up on review. It shifts financial liability to the patient if Medicare denies the claim; it does not apply to commercial payers, which have their own separate financial-responsibility processes.
Verify before billing. CPT is a registered trademark of the American Medical Association; codes here are paraphrased, not reproduced from the CPT Professional edition. CPT, HCPCS and ICD-10 codes, coverage policy, and bundling edits change, including annual code-set updates. This page reflects standard industry practice and is provided for general education — it is not a substitute for your own compliance review, your current payer contracts, or the current-year code sets. Confirm requirements against your specific payer mix before submitting claims.