feat: beneficiary cost sharing notebook — coinsurance trends and CY2026 impact

Tracks skin substitute beneficiary out-of-pocket costs over time:

1. Application fee coinsurance by region (20% of PFS carrier fee)
2. Product coinsurance trajectory (20% of ASP+6% per cm²)
3. Total episode cost sharing for 25cm² wound (product + application)
4. OPPS copayment collapse: $105-366 (2021-2025) → $25.43 flat (2026)
5. Winners/losers: high-ASP products save, low-ASP products pay more
6. Episode scenarios: Apligraf, EpiFix, GrafixCore before/after CY2026
7. Part B deductible context ($147 in 2015 → $257 in 2025-2026)
8. Key takeaways

refs #246

notebooks/skin_sub_cost_sharing.py

@@ -0,0 +1,512 @@
+import marimo
+
+__generated_with = "0.21.1"
+app = marimo.App(width="medium")
+
+
+@app.cell(hide_code=True)
+def _():
+    import marimo as mo
+
+    return (mo,)
+
+
+@app.cell(hide_code=True)
+def _(mo):
+    mo.md("""
+    # Beneficiary Cost Sharing for Skin Substitutes
+
+    Medicare Part B beneficiaries pay **20% coinsurance** on both the
+    application procedure (PFS) and the product (ASP + 6%). This
+    notebook tracks how cost sharing has changed over time and how
+    the CY2026 reclassification affects out-of-pocket exposure.
+
+    **Cost-sharing components:**
+    - **Application fee**: 20% of PFS carrier locality fee (15271–15278)
+    - **Product cost**: 20% of ASP + 6% payment limit × units
+    - **OPPS copayment**: minimum unadjusted copayment per APC (hospital outpatient)
+    - **Limiting charge**: non-participating providers may charge up to 115% of fee schedule
+
+    **CY2026 change:** All skin subs move to a flat $127.28/cm². OPPS copay
+    drops from ~$165–$366 per code to $25.43 flat. Product coinsurance
+    collapses to $25.43/unit regardless of actual ASP.
+    """)
+    return
+
+
+@app.cell(hide_code=True)
+def _():
+    import altair as alt
+    import polars as pl
+    from conf import connect
+    from pfs.rules import RULES
+
+    con = connect.duckdb()
+
+    def q(sql):
+        return con.execute(sql).pl()
+
+    SKIN_CODES = "('15271','15272','15273','15274','15275','15276','15277','15278')"
+
+    # Part B deductible history (published by CMS annually)
+    DEDUCTIBLES = {
+        2015: 147.00, 2016: 166.00, 2017: 183.00, 2018: 183.00,
+        2019: 185.00, 2020: 198.00, 2021: 203.00, 2022: 233.00,
+        2023: 226.00, 2024: 240.00, 2025: 257.00, 2026: 257.00,
+    }
+
+    return DEDUCTIBLES, RULES, SKIN_CODES, alt, con, pl, q
+
+
+# ── 1. Application fee coinsurance over time ─────────────────────────
+
+
+@app.cell(hide_code=True)
+def _(mo):
+    mo.md("""
+    ## 1. Application Fee Coinsurance by Region
+
+    The beneficiary pays 20% of the PFS-approved amount for the
+    application procedure. This varies by locality and year.
+    """)
+    return
+
+
+@app.cell(hide_code=True)
+def _(alt, q):
+    regions = [
+        "MANHATTAN", "REST OF FLORIDA", "REST OF TEXAS",
+        "REST OF CALIFORNIA", "SOUTH CAROLINA",
+    ]
+    region_list = ", ".join(f"'{r}'" for r in regions)
+
+    app_coinsurance = q(f"""
+        SELECT c.year, g.locality_name,
+               c.non_fac_fee,
+               round(c.non_fac_fee * 0.20, 2) as bene_coinsurance,
+               c.non_fac_limiting_charge,
+               round(c.non_fac_limiting_charge * 0.20, 2) as bene_limiting_coinsurance
+        FROM pfs.carrier_locality c
+        JOIN pfs.gpci g ON c.mac = g.mac AND c.locality = g.locality AND c.year = g.year
+        WHERE c.hcpcs = '15271'
+          AND g.locality_name IN ({region_list})
+        ORDER BY c.year, g.locality_name
+    """)
+
+    app_chart = (
+        alt.Chart(app_coinsurance.to_pandas())
+        .mark_line(point=True)
+        .encode(
+            x=alt.X("year:O", title="Year"),
+            y=alt.Y("bene_coinsurance:Q", title="Beneficiary Coinsurance ($)"),
+            color=alt.Color("locality_name:N", title="Region"),
+            tooltip=["year", "locality_name", "non_fac_fee",
+                     "bene_coinsurance", "non_fac_limiting_charge"],
+        )
+        .properties(
+            title="15271 Application — Beneficiary 20% Coinsurance by Region",
+            width=700, height=350,
+        )
+    )
+    app_chart
+    return
+
+
+# ── 2. Product coinsurance trajectory ────────────────────────────────
+
+
+@app.cell(hide_code=True)
+def _(mo):
+    mo.md("""
+    ## 2. Product Coinsurance Over Time (Per Unit)
+
+    The beneficiary pays 20% of the ASP + 6% payment limit **per cm²**.
+    For high-ASP products, this adds up fast — a 25cm² application of
+    a $150/cm² product means $750 in coinsurance just for the product.
+
+    The red dashed line shows the CY2026 flat-rate coinsurance:
+    20% × $127.28 = **$25.46/cm²**.
+    """)
+    return
+
+
+@app.cell(hide_code=True)
+def _(alt, pl, q):
+    product_coins = q("""
+        SELECT quarter, hcpcs_code, short_description,
+               payment_limit,
+               round(payment_limit * 0.20, 2) as bene_per_unit
+        FROM skin_subs.asp_quarterly
+        WHERE hcpcs_code IN ('Q4101','Q4186','Q4132','Q4116','Q4100')
+        ORDER BY quarter, hcpcs_code
+    """)
+
+    flat_coins = (
+        alt.Chart(pl.DataFrame({"y": [127.28 * 0.20]}).to_pandas())
+        .mark_rule(color="red", strokeDash=[4, 4], strokeWidth=2)
+        .encode(y="y:Q")
+    )
+
+    product_lines = (
+        alt.Chart(product_coins.to_pandas())
+        .mark_line()
+        .encode(
+            x=alt.X("quarter:O", title="Quarter",
+                     axis=alt.Axis(labelAngle=-45, labelFontSize=8)),
+            y=alt.Y("bene_per_unit:Q", title="Beneficiary Coinsurance per cm² ($)"),
+            color=alt.Color("short_description:N", title="Product"),
+            tooltip=["quarter", "hcpcs_code", "short_description",
+                     "payment_limit", "bene_per_unit"],
+        )
+    )
+
+    product_chart = (
+        (product_lines + flat_coins)
+        .properties(
+            title="Product Coinsurance per Unit (20% of ASP + 6%)",
+            width=700, height=400,
+        )
+    )
+    product_chart
+    return
+
+
+# ── 3. Total episode cost sharing ────────────────────────────────────
+
+
+@app.cell(hide_code=True)
+def _(mo):
+    mo.md("""
+    ## 3. Total Episode Cost Sharing (25cm² Wound)
+
+    For a typical 25cm² wound treated in an office setting, the
+    beneficiary's total out-of-pocket is:
+
+    ```
+    total = 20% × application_fee + 20% × (ASP+6% × 25 units)
+    ```
+
+    This chart shows how that total has changed over time for
+    selected products, with the post-2026 flat-rate equivalent shown.
+    """)
+    return
+
+
+@app.cell(hide_code=True)
+def _(alt, pl, q):
+    # Use Q1 of each year for annual comparison
+    episode_sharing = q("""
+        WITH asp_annual AS (
+            SELECT CAST(substr(quarter, 1, 4) AS INTEGER) as year,
+                   hcpcs_code, short_description,
+                   payment_limit
+            FROM skin_subs.asp_quarterly
+            WHERE substr(quarter, 6, 2) = 'Q1'
+              AND hcpcs_code IN ('Q4101','Q4186','Q4132','Q4116')
+        ),
+        app_fee AS (
+            SELECT c.year, avg(c.non_fac_fee) as avg_app_fee
+            FROM pfs.carrier_locality c
+            WHERE c.hcpcs = '15271'
+            GROUP BY c.year
+        )
+        SELECT a.year, a.hcpcs_code, a.short_description,
+               round(a.payment_limit, 2) as asp_per_unit,
+               round(f.avg_app_fee, 2) as avg_app_fee,
+               round(f.avg_app_fee * 0.20, 2) as app_coinsurance,
+               round(a.payment_limit * 25 * 0.20, 2) as product_coinsurance_25cm,
+               round(f.avg_app_fee * 0.20 + a.payment_limit * 25 * 0.20, 2) as total_bene_cost
+        FROM asp_annual a
+        LEFT JOIN app_fee f ON a.year = f.year
+        ORDER BY a.year, a.hcpcs_code
+    """)
+
+    flat_episode = 127.28 * 25 * 0.20  # $636.40 product + ~$28 application
+
+    flat_line = (
+        alt.Chart(pl.DataFrame({"y": [flat_episode]}).to_pandas())
+        .mark_rule(color="red", strokeDash=[4, 4], strokeWidth=2)
+        .encode(y="y:Q")
+    )
+
+    episode_lines = (
+        alt.Chart(episode_sharing.to_pandas())
+        .mark_line(point=True)
+        .encode(
+            x=alt.X("year:O", title="Year"),
+            y=alt.Y("total_bene_cost:Q",
+                     title="Beneficiary Total Cost Sharing ($)"),
+            color=alt.Color("short_description:N", title="Product"),
+            tooltip=["year", "hcpcs_code", "short_description",
+                     "asp_per_unit", "app_coinsurance",
+                     "product_coinsurance_25cm", "total_bene_cost"],
+        )
+    )
+
+    episode_chart = (
+        (episode_lines + flat_line)
+        .properties(
+            title="Total Beneficiary Cost Sharing — 25cm² Wound Episode",
+            width=700, height=400,
+        )
+    )
+    episode_chart
+    return
+
+
+# ── 4. OPPS copayment collapse ───────────────────────────────────────
+
+
+@app.cell(hide_code=True)
+def _(mo):
+    mo.md("""
+    ## 4. OPPS Copayment Collapse in CY2026
+
+    In the hospital outpatient setting (HOPD), beneficiaries pay a
+    minimum unadjusted copayment per APC. For skin substitutes:
+
+    - **2021–2025**: Copays ranged from $105–$366 depending on the
+      product's APC assignment (high-cost vs. low-cost categories)
+    - **CY2026**: All products reclassified to a single flat rate
+      with copay of **$25.43** — a >85% reduction
+
+    This is the most dramatic beneficiary cost-sharing change in
+    the CY2026 reclassification.
+    """)
+    return
+
+
+@app.cell(hide_code=True)
+def _(alt, q):
+    opps_copay = q("""
+        SELECT year,
+               count(*) as products,
+               round(avg(minimum_unadjusted_copayment), 2) as avg_copay,
+               round(min(minimum_unadjusted_copayment), 2) as min_copay,
+               round(max(minimum_unadjusted_copayment), 2) as max_copay,
+               round(max(minimum_unadjusted_copayment) -
+                     min(minimum_unadjusted_copayment), 2) as copay_spread
+        FROM opps.skin_sub_addendum_b
+        WHERE minimum_unadjusted_copayment > 0
+        GROUP BY year ORDER BY year
+    """)
+
+    copay_chart = (
+        alt.Chart(opps_copay.to_pandas())
+        .mark_bar()
+        .encode(
+            x=alt.X("year:O", title="Year"),
+            y=alt.Y("avg_copay:Q", title="Average OPPS Copayment ($)"),
+            color=alt.condition(
+                alt.datum.year == 2026,
+                alt.value("#2ca02c"),
+                alt.value("#1f77b4"),
+            ),
+            tooltip=["year", "products", "avg_copay", "min_copay",
+                     "max_copay", "copay_spread"],
+        )
+        .properties(
+            title="OPPS Minimum Unadjusted Copayment — Skin Substitutes",
+            width=700, height=300,
+        )
+    )
+
+    mo.vstack([copay_chart, opps_copay])
+    return
+
+
+# ── 5. Winners and losers: beneficiary perspective ────────────────────
+
+
+@app.cell(hide_code=True)
+def _(mo):
+    mo.md("""
+    ## 5. Beneficiary Impact: Who Pays More, Who Pays Less?
+
+    Under the flat rate, beneficiaries using **high-ASP products**
+    (EpiFix, GrafixCore) see their per-unit coinsurance drop
+    dramatically. Those using **low-ASP products** (Apligraf at
+    ~$30/unit) see coinsurance rise from ~$6 to ~$25.
+
+    This is a wealth transfer: beneficiaries who previously used
+    expensive products benefit; those with cheaper products pay more.
+    """)
+    return
+
+
+@app.cell(hide_code=True)
+def _(alt, q):
+    bene_impact = q("""
+        SELECT hcpcs_code, short_description,
+               payment_limit as current_asp_payment,
+               round(payment_limit * 0.20, 2) as current_bene_per_unit,
+               127.28 as flat_rate,
+               round(127.28 * 0.20, 2) as flat_bene_per_unit,
+               round(127.28 * 0.20 - payment_limit * 0.20, 2) as bene_delta_per_unit,
+               CASE
+                   WHEN payment_limit * 0.20 > 127.28 * 0.20 THEN 'bene saves'
+                   WHEN payment_limit * 0.20 < 127.28 * 0.20 THEN 'bene pays more'
+                   ELSE 'neutral'
+               END as bene_impact
+        FROM skin_subs.asp_quarterly
+        WHERE quarter = (SELECT max(quarter) FROM skin_subs.asp_quarterly)
+        ORDER BY bene_delta_per_unit
+    """)
+
+    bene_chart = (
+        alt.Chart(bene_impact.to_pandas())
+        .mark_bar()
+        .encode(
+            x=alt.X("bene_delta_per_unit:Q",
+                     title="Change in Beneficiary Coinsurance per Unit ($)"),
+            y=alt.Y("short_description:N", title="", sort="x",
+                     axis=alt.Axis(labelLimit=300)),
+            color=alt.Color("bene_impact:N",
+                            scale=alt.Scale(
+                                domain=["bene saves", "bene pays more", "neutral"],
+                                range=["#2ca02c", "#d62728", "#7f7f7f"],
+                            ),
+                            title="Impact"),
+            tooltip=["hcpcs_code", "short_description",
+                     "current_bene_per_unit", "flat_bene_per_unit",
+                     "bene_delta_per_unit"],
+        )
+        .properties(
+            title="CY2026 Beneficiary Coinsurance Change per Unit",
+            width=700,
+        )
+    )
+    bene_chart
+    return
+
+
+# ── 6. Episode scenario comparison ───────────────────────────────────
+
+
+@app.cell(hide_code=True)
+def _(mo):
+    mo.md("""
+    ## 6. Episode Scenarios: Before vs. After CY2026
+
+    Three wound scenarios showing the complete beneficiary cost
+    breakdown before and after the flat-rate reclassification.
+    All assume office setting (POS 11), participating provider,
+    national average application fee.
+    """)
+    return
+
+
+@app.cell(hide_code=True)
+def _(pl, q):
+    # Get average national app fee for 2025
+    avg_fee = q("""
+        SELECT round(avg(non_fac_fee), 2) as avg_fee
+        FROM pfs.carrier_locality
+        WHERE year = 2025 AND hcpcs = '15271'
+    """).item()
+
+    scenarios = pl.DataFrame({
+        "scenario": [
+            "Small wound (10cm²) — Q4101 Apligraf",
+            "Medium wound (25cm²) — Q4186 EpiFix",
+            "Large wound (50cm²) — Q4132 GrafixCore",
+        ],
+        "units": [10, 25, 50],
+        "asp_per_unit": [30.23, 151.17, 106.70],
+        "product_name": ["Apligraf", "EpiFix", "GrafixCore"],
+    }).with_columns(
+        # Pre-2026: ASP + 6%
+        (pl.col("asp_per_unit") * pl.col("units") * 0.20).round(2).alias("pre_product_coins"),
+        pl.lit(avg_fee * 0.20).round(2).alias("pre_app_coins"),
+        # Post-2026: flat $127.28
+        (pl.lit(127.28) * pl.col("units") * 0.20).round(2).alias("post_product_coins"),
+        pl.lit(avg_fee * 0.20).round(2).alias("post_app_coins"),
+    ).with_columns(
+        (pl.col("pre_product_coins") + pl.col("pre_app_coins")).alias("pre_total"),
+        (pl.col("post_product_coins") + pl.col("post_app_coins")).alias("post_total"),
+    ).with_columns(
+        (pl.col("post_total") - pl.col("pre_total")).round(2).alias("delta"),
+    )
+    scenarios
+    return
+
+
+# ── 7. Part B deductible context ─────────────────────────────────────
+
+
+@app.cell(hide_code=True)
+def _(mo):
+    mo.md("""
+    ## 7. Part B Deductible Context
+
+    Before coinsurance applies, beneficiaries must meet the annual
+    Part B deductible. A single skin substitute episode can exceed
+    the entire deductible, meaning the full coinsurance amount is
+    additional out-of-pocket cost for most beneficiaries.
+    """)
+    return
+
+
+@app.cell(hide_code=True)
+def _(DEDUCTIBLES, alt, pl):
+    deductible_df = pl.DataFrame({
+        "year": list(DEDUCTIBLES.keys()),
+        "deductible": list(DEDUCTIBLES.values()),
+    })
+
+    ded_chart = (
+        alt.Chart(deductible_df.to_pandas())
+        .mark_bar(color="#ff7f0e")
+        .encode(
+            x=alt.X("year:O", title="Year"),
+            y=alt.Y("deductible:Q", title="Annual Part B Deductible ($)"),
+            tooltip=["year", "deductible"],
+        )
+        .properties(
+            title="Medicare Part B Annual Deductible",
+            width=700, height=250,
+        )
+    )
+    ded_chart
+    return
+
+
+# ── 8. Key takeaways ─────────────────────────────────────────────────
+
+
+@app.cell(hide_code=True)
+def _(mo):
+    mo.md("""
+    ## 8. Key Takeaways
+
+    1. **OPPS copay drops >85% in CY2026.** From $105–$366 per code
+       to $25.43 flat. This is the single largest beneficiary-facing
+       change in the reclassification.
+
+    2. **High-ASP product users save significantly.** For EpiFix
+       (Q4186, ~$151/unit), coinsurance per cm² drops from ~$30 to
+       ~$25 — but for a 25cm² wound, the total product coinsurance
+       drops from ~$755 to ~$636 ($119 savings).
+
+    3. **Low-ASP product users pay more.** For Apligraf (Q4101,
+       ~$30/unit), per-unit coinsurance rises from ~$6 to ~$25.
+       A 25cm² wound goes from ~$30 to ~$636 in product coinsurance.
+
+    4. **Application fee coinsurance is stable.** The PFS component
+       (~$27–$35 for 15271 depending on locality) is a small fraction
+       of total cost sharing and relatively stable over time.
+
+    5. **Deductible is a floor, not a ceiling.** The $257 Part B
+       deductible (2025–2026) is typically exceeded by a single skin
+       sub episode, so coinsurance applies to the full amount.
+
+    6. **No Medigap/supplement analysis.** Most beneficiaries have
+       supplemental coverage (Medigap, employer, Medicaid dual) that
+       covers the 20% coinsurance. Actual out-of-pocket may be lower
+       depending on coverage type.
+    """)
+    return
+
+
+if __name__ == "__main__":
+    app.run()