2026 ICD-10-CM Diagnosis Code T78.8XXSOther adverse effects, not elsewhere classified, sequela

ICD-10-CM Codes›S00–T88›T66-T78›T78

ICD-10-CM T78.8XXS
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

T78.8XXS is a billable ICD-10-CM diagnosis code for other adverse effects, not elsewhere classified, sequela. The 7th character S marks it as a sequela code, which reports a problem that remains after the original condition has resolved. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 922 through 923. The code is exempt from POA reporting. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Poisoning/toxic effect/adverse effects/underdosing, sequela.

Code Identity

ICD-10-CM Code
T78.8XXS
Billable Status
Yes — Valid for Submission
Code Describes
Other adverse effects, not elsewhere classified, sequela
Short Description
Other adverse effects, not elsewhere classified, sequela
Same as the full description in the CMS dataset.
Parent Code
T78.8
Other adverse effects, not elsewhere classified

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionT66-T78Other and unspecified effects of external causes
CategoryT78Adverse effects, not elsewhere classified
This CodeT78.8XXSOther adverse effects, not elsewhere classified, sequela

Present on Admission (POA)Billing

T78.8XXS is exempt from POA reporting on inpatient claims to general acute care hospitals. Review other POA exempt codes.

Coding GuidelinesGuidance

The appropriate 7th character is to be added to each code from block Adverse effects, not elsewhere classified (T78). Use the following options for the applicable episode of care:

  • A - initial encounter
  • D - subsequent encounter
  • S - sequela

Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2026, published by CMS and the National Center for Health Statistics.

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR INJ075
Poisoning/toxic effect/adverse effects/underdosing, sequela
Default principal diagnosis: inpatient Yes · outpatient Yes

Convert T78.8XXS to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
909.9 Late eff exter cause NEC
Approximate The match is approximate rather than exact.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About T78.8XXSOverview

Is T78.8XXS (Other adverse effects, not elsewhere classified) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report other adverse effects, not elsewhere classified, sequela on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What does the 7th character S in T78.8XXS mean?

The final character S makes this a sequela code: it reports a lingering problem that remains after the other adverse effects, not elsewhere classified itself has resolved, not the original event.

What MS-DRG does T78.8XXS group to?

When other adverse effects, not elsewhere classified, sequela is the principal diagnosis on an inpatient stay, it groups to MS-DRG 922, 923, with relative weights from 1.0177 to 1.7494 depending on complications. Higher weights mean higher Medicare reimbursement.

Is T78.8XXS exempt from POA reporting?

Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for other adverse effects, not elsewhere classified, sequela on inpatient claims.

What is the ICD-9 equivalent of T78.8XXS?

Under the General Equivalence Mappings, other adverse effects, not elsewhere classified, sequela converts to ICD-9-CM 909.9 (late eff exter cause NEC). The mapping is approximate, so confirm the match fits the documentation.

Footnotes

[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.