CSTM & APR-DRG

Late-stage fallback imputations. CSTM maps payer-specific CSTM-ALL codes from core_rates onto standard billing codes; APR-DRG uses the crosswalk from MS-DRG outputs.

CSTM (Custom All)

Some payers publish rates in their MRF under a non-standard billing_code_type = 'CSTM-ALL' rather than per HCPCS or DRG code. CSTM imputations read those entries and map them onto the standard Rate Object Space.

Active payers: UHC (payer_id = 643) and Cigna (payer_id = 76).

UHC

UHC publishes CSTM-ALL codes (e.g. CSTMALL-001) that each correspond to one or more HCPCS billing codes. The pipeline resolves them using a crosswalk table:

• Crosswalk: CSTM_ALL_XWALK_TABLE (tq_intermediate.cld_utils.cstm_all) — maps each CSTM-ALL code → HCPCS billing_code
• Rate types handled: negotiated, percentage, per diem
• Output columns: cstm_negotiated_rate, cstm_percentage_rate, cstm_per_diem_rate (and cstm_per_diem_mult_glos for per-diem × Medicare GLOS)
• Scope: Outpatient HCPCS

Cigna

Cigna uses a single catch-all billing code (CSTM00) that applies a percentage rate to all Inpatient and Outpatient ROIDs. The additional_information field determines routing:

additional_information value	Maps to
'Inpatient services not otherwise priced'	billing_code_type = 'MS-DRG', bill_type = 'Inpatient'
'Outpatient services not otherwise priced'	billing_code_type = 'HCPCS', bill_type = 'Outpatient'

• Rate type: percentage only
• The xwalk for Cigna is generated inline from rate_object_space — every Inpatient/Outpatient ROID in the provider's ROS is a potential target

Output

Both payers write to tmp_int_imputations_cstm, partitioned by payer_id.

APR-DRG Imputations

APR-DRG (All Patient Refined DRG) is an alternative DRG classification system used by some payers. Clear Rates handles it as a final fallback:

1

Filter rate_object_space

Identify all ROIDs with billing_code_type = APR-DRG.

→ rate_object_space (APR-DRG subset)

2

Aggregate via crosswalk

Apply the APR-DRG → MS-DRG crosswalk to aggregate derived and CSTM imputations computed for MS-DRG equivalents.

→ tmp_int_imputations_derived, tmp_int_imputations_cstm

3

Join gross charges

Join gross charge data for the APR-DRG ROID to enable percentage-based rate derivation where applicable.

4

Output

Final APR-DRG imputed rates written to output table.

→ tmp_int_imputations_aprdrg

Imputation order matters

The full imputation sequence is: Main → MS-DRG base rates → Derived → CSTM → APR-DRG. Each stage can use outputs from previous stages — for example, APR-DRG imputations rely on derived and CSTM outputs computed earlier. CSTM and APR-DRG are last resorts — they only activate when earlier stages found nothing for a given ROID.