ICD-10-CM Official Guidelines for Coding and Reporting FY 2026

Flashcards covering the essential vocabulary, coding conventions, and specific disease guidelines from the ICD-10-CM FY 2026 official document.

Cooperating Parties for the ICD-10-CM

The four organizations that approve the coding guidelines: the American Hospital Association (AHA), the American Health Information Management Association (AHIMA), CMS, and NCHS.

Provider

In the context of the guidelines, this refers to a physician or any qualified health care practitioner who is legally accountable for establishing the patient’s diagnosis.

NEC (Not Elsewhere Classifiable)

An abbreviation representing "other specified." It is used when a specific code is not available for a condition, directing the coder to the "other specified" code in the Tabular List.

NOS (Not Otherwise Specified)

An abbreviation equivalent to "unspecified."

Nonessential Modifiers

Supplementary words enclosed in parentheses in both the Alphabetic Index and Tabular List that may be present or absent in the statement of a disease without affecting the code number.

Excludes1

A pure "NOT CODED HERE!" note indicating that the code excluded should never be used at the same time as the code above it, used when two conditions cannot occur together (e.g., congenital vs. acquired).

Excludes2

A note meaning "Not included here," indicating that the condition excluded is not part of the condition represented by the code, but the patient may have both conditions at the same time.

Etiology/Manifestation Convention

A coding convention for conditions with both an underlying etiology and body system manifestations, requiring the underlying condition to be sequenced first followed by the manifestation.

Default Code

The code listed next to a main term in the Alphabetic Index, representing the condition most commonly associated with that term or the unspecified code for the condition.

Combination Code

A single code used to classify two diagnoses, a diagnosis with an associated secondary process (manifestation), or a diagnosis with an associated complication.

Sequela (Late Effect)

The residual effect (condition produced) after the acute phase of an illness or injury has terminated, with no time limit on when it can be used.

Laterality

ICD-10-CM codes that specify whether a condition occurs on the left side, right side, or is bilateral.

Z21

The ICD-10-CM code for Asymptomatic human immunodeficiency virus [HIV] infection status, used when a patient is HIV positive without symptoms.

Urosepsis

A nonspecific term that is not synonymous with sepsis and has no default code in the Alphabetic Index; the provider must be queried for clarification.

Septic Shock

Circulatory failure associated with severe sepsis, representing a type of acute organ dysfunction.

Colonization

Also called "carriage," meaning that MSSA or MRSA is present on or in the body without necessarily causing illness.

U07.1

The ICD-10-CM code assigned for a confirmed diagnosis of COVID-19 as documented by the provider.

MIS (Multisystem Inflammatory Syndrome)

A condition identified by code M35.81, which may be associated with a current or previous COVID-19 infection.

BIA-ALCL

Breast Implant Associated Anaplastic Large Cell Lymphoma, a type of lymphoma (code C84.7A) that can develop around breast implants.

Rule of Nines

A method used to estimate the body surface involved in burns/corrosions: head and neck $9\%$, each arm $9\%$, each leg $18\%$, anterior trunk $18\%$, posterior trunk $18\%$, and genitalia $1\%.$

Adverse Effect

A reaction occurring when a drug has been correctly prescribed and properly administered, coded by the nature of the effect followed by the T-code with a 5th or 6th character of "5".

Poisoning

A reaction to the improper use of a medication, such as an overdose, wrong substance given, or wrong route of administration.

Underdosing

Taking less of a medication than is prescribed by a provider or a manufacturer’s instruction.

Principal Diagnosis

The condition established after study to be chiefly responsible for occasioning the admission of the patient to the hospital for care.

Peripartum Period

The timeframe defined from the last month of pregnancy to five months postpartum.

Postpartum Period

The timeframe beginning immediately after delivery and continuing for six weeks following delivery.

Present on Admission (POA)

A condition present at the time the order for inpatient admission occurs, including conditions that develop during an outpatient encounter prior to the admission order.