Chapter 33 — Key Takeaways

The design

Since October 1, 1983, Medicare pays acute care hospitals per classified stay, not per service. One predetermined payment per discharge, set by the MS-DRG the coded record groups to. The UB-04 still carries every charge; the money reads FL 67 and FL 74 — diagnoses, POA indicators, procedures. On an inpatient claim, the coding is the pricing.

Principal diagnosis (inpatient)

The condition established AFTER STUDY to be chiefly responsible for OCCASIONING THE ADMISSION. (UHDDS; Guidelines Section II.)

• Not the presenting symptom · not the most severe condition · never anything that developed after admission
• Two conditions equally responsible → either may lead (real, narrow discretion)
• "Probable/suspected/likely" at discharge → coded as established (Ch. 9 §9.5 — opposite of outpatient)
• Secondary diagnoses have their own test: Section III — evaluated, treated, worked up, extended the stay, increased care

Severity: CC and MCC

Account 22-8891: J44.1 principal; J96.01 (acute respiratory failure with hypoxia, POA = Y) is the MCC → DRG 190.

The grouper and the money

Pipeline: pre-MDC check → principal dx maps the MDC → surgical partition (OR-designated ICD-10-PCS code?) → severity split.

Payment = relative weight × base rate (labor share × wage index + non-labor). All figures constructed; verify in the current IPPS final rule:

   base rate $6,200.00
   DRG 190  COPD w/ MCC        1.1015   $6,829.30
   DRG 191  COPD w/ CC         0.8003   $4,961.86
   DRG 192  COPD w/o CC/MCC    0.6555   $4,064.10

   the MCC's value   190 − 191 = $1,867.44
   the CC's value    191 − 192 =   $897.76

Length of stay and charges do not change the payment — except through outliers (§33.8) and the cost-to-charge ratio inside them.

CMI, POA, transfers

• Case mix index = average relative weight of discharges = revenue per case at a fixed base rate. It cannot distinguish sicker patients from better documentation. Diagnostic, never target.
• POA: Y · N · U (counted against the hospital) · W (honored) · exempt. From the record's chronology, never from the payment consequence.
• Transfer rule (kept from Ch. 26 §26.7): stay ≥ 1 day below GMLOS + qualifying discharge status → per diem = full DRG ÷ GMLOS, day 1 doubled, capped at the full DRG. Post-acute version: defined DRG list, annually revised. The rule reads FL 17 — reconcile it against the discharge summary.
• GMLOS vs AMLOS: geometric mean resists outlier skew; the payment rules key on it.

ICD-10-PCS (structural level)

Seven characters, table-built, no I or O, updated October 1: section · body system · root operation · body part · approach · device · qualifier. The root operation codes the documented objective (Excision = portion; Resection = all of a body part; Replacement, Insertion, Extirpation, Dilation, Drainage…), never the procedure's title. PCS feeds the surgical partition — a character error can be a different DRG.

The chapter's number

\$1,867.44 — the value of "acute respiratory failure with hypoxia" written, versus "hypoxic" written, on the same patient. The gap record is not wrong; it is unwritten — the model finding from Ch. 14 §14.4, now with an MCC attached. The remedy is the CDI query (Ch. 38 §38.3), asked in both directions. The accurate record and the defensible record are the same record.

Monday morning

You should be able to: select a principal diagnosis under the inpatient rules and defend the sequencing; run a record through the four grouper steps by hand; compute weight × base rate and the tier differences; assign every POA indicator from the record's chronology; apply the transfer rule's per-diem arithmetic to a short-stay transfer; read a seven-character PCS code position by position; and explain to anyone in the building — accurately, without cynicism — why one documented sentence was worth \$1,867.44.