Skip to main content
MS-DRG 998 · MDC · Medical

MS-DRG 998: Principal Diagnosis Invalid As Discharge Diagnosis

Reviewed by QuickIntell RCM Editorial Team · Last reviewed

Data effective
Data currency: IPPS Table 5 FY2027 final rule (effective October 1, 2026); Definitions Manual v44 (effective October 1, 2026). Next CMS release: April 1, 2027 (v44.1 mid-year update), then the FY2028 final rule in August 2027.

Key facts for DRG 998

FY2027 relative weight
n/a
Change vs FY2026
n/a
FY2026 weight n/a
Geometric mean LOS
n/a days
Arithmetic mean n/a days
MDC
None
Not assigned to an MDC
Severity level
single severity level
Transfer policy
Not a transfer DRG

TL;DR

MS-DRG 998 is a medical group in MDC (Not assigned to an MDC) at a single-severity group of its family. CMS assigns it a FY2027 relative weight of n/a with a geometric mean length of stay of n/a days and an arithmetic mean of n/a. A prior-year weight is not available for comparison. CMS does not split this group by severity. The v44 Definitions Manual assigns it through 279 principal diagnosis codes.

What changed from FY2026 to FY2027

CMS recalibrates every MS-DRG weight annually from the prior year's MedPAR claims. For DRG 998 the FY2027 relative weight is n/a against n/a in FY2026, a fall of 0.00%.

FY2026 versus FY2027 payment factors for MS-DRG 998
MetricFY2026FY2027Change
Relative weightn/an/an/a
Geometric mean LOS (days)n/an/an/a
Arithmetic mean LOS (days)n/an/an/a
Weights shown are the FY2027 final values after the 10% cap on year-over-year reductions where applicable.

CC and MCC family

DRG 998 stands alone: CMS does not split this base group by CC or MCC severity, so complication documentation does not move the assignment, although it still affects quality and risk-adjustment reporting.

Grouper logic (v44 Definitions Manual)

Principal Diagnosis: 279 ICD-10 codes drive assignment to this group; the first 12 are shown.

Principal Diagnosis codes assigned to DRG 998 (sample)
ICD-10 codeDescription
O0900Supervision of pregnancy with history of infertility, unspecified trimester
O0901Supervision of pregnancy with history of infertility, first trimester
O0902Supervision of pregnancy with history of infertility, second trimester
O0903Supervision of pregnancy with history of infertility, third trimester
O0910Supervision of pregnancy with history of ectopic pregnancy, unspecified trimester
O0911Supervision of pregnancy with history of ectopic pregnancy, first trimester
O0912Supervision of pregnancy with history of ectopic pregnancy, second trimester
O0913Supervision of pregnancy with history of ectopic pregnancy, third trimester
O09211Supervision of pregnancy with history of pre-term labor, first trimester
O09212Supervision of pregnancy with history of pre-term labor, second trimester
O09213Supervision of pregnancy with history of pre-term labor, third trimester
O09219Supervision of pregnancy with history of pre-term labor, unspecified trimester

Documentation and denial exposure

As a medical DRG, assignment depends on the principal diagnosis sequenced from the attending's documentation; a secondary condition sequenced first, or a symptom code in place of the confirmed diagnosis, changes the MDC or the DRG. Because this family has no severity split, review risk concentrates on medical-necessity of the admission itself and on the two-midnight benchmark. Typical inpatient denial codes for this group: CARC 16 (claim lacks information needed to group the stay), CARC 50 (the admission or procedure is judged not medically necessary), CARC 97 (a service is bundled into the DRG payment).

How QuickIntell uses DRG 998 data

QuickCode groups inpatient encounters against the current v44 logic, flags CC and MCC candidates that lack supporting documentation, and shows the weight difference across the family before the claim drops. QuickScribe captures the attending's language that supports severity, and QuickRCM works DRG-validation denials with the grouper evidence attached.

Explore QuickCodeExplore QuickScribeBook a meeting

Frequently asked questions — DRG 998

What is MS-DRG 998?

MS-DRG 998 is "Principal Diagnosis Invalid As Discharge Diagnosis", a medical Medicare Severity Diagnosis-Related Group in MDC , Not assigned to an MDC. Medicare pays inpatient stays grouped here at the hospital's base rate multiplied by the DRG relative weight.

What is the FY2027 relative weight for DRG 998?

The FY2027 relative weight is n/a (IPPS final rule Table 5, effective October 1, 2026).

What is the average length of stay for DRG 998?

CMS reports a geometric mean length of stay of n/a days and an arithmetic mean of n/a days for FY2027. The geometric mean is used for transfer-payment calculations.

What documentation supports the severity level of DRG 998?

DRG 998 has no CC or MCC sibling, so secondary-diagnosis capture does not change the group or its weight. Review effort belongs instead on the principal diagnosis sequencing and the procedure codes that place the stay in this group, and on medical necessity of the inpatient admission itself under the two-midnight benchmark, which is where denials for single-severity groups concentrate.

Which codes group to DRG 998?

The v44 Definitions Manual lists 279 principal diagnosis codes for this group. Examples from the principal diagnosis list: O0900 (Supervision of pregnancy with history of infertility, unspecified trimester); O0901 (Supervision of pregnancy with history of infertility, first trimester); O0902 (Supervision of pregnancy with history of infertility, second trimester); O0903 (Supervision of pregnancy with history of infertility, third trimester).

Is DRG 998 a post-acute transfer DRG?

No. DRG 998 is not on the FY2027 post-acute care transfer list, so the transfer per-diem policy does not apply to it.

Sources

Every figure on this page is taken from the CMS publications below, as released by the Centers for Medicare & Medicaid Services. Projection built 2026-10-02. Verify against the primary file before billing or contracting decisions.

Disclaimer

This page is an operational reference compiled from the CMS IPPS FY2027 final rule (Table 5) and the v44 ICD-10 MS-DRG Definitions Manual. Relative weights are national factors; actual payment depends on each hospital's wage-adjusted base rate, add-ons, outliers and transfer adjustments. Nothing here is legal, clinical or billing advice; verify grouping against your encoder and the published CMS files.