Section IV. Diagnostic Coding and Reporting Guidelines for Outpatient Services

These coding guidelines for outpatient diagnoses have been approved for use by hospitals/ providers in coding and reporting hospital-based outpatient services and provider-based office visits. Guidelines in Section I, Conventions, general coding guidelines and chapter-specific guidelines, should also be applied for outpatient services and office visits. Information about the use of certain abbreviations, punctuation, symbols, and other conventions used in the ICD-10-CM Tabular List (code numbers and titles), can be found in Section IA of these guidelines, under "Conventions Used in the Tabular List." Section I.B. contains general guidelines that apply to the entire classification. Section I.C. contains chapter-specific guidelines that correspond to the chapters as they are arranged in the classification. Information about the correct sequence to use in finding a code is also described in Section I. The terms encounter and visit are often used interchangeably in describing outpatient service contacts and, therefore, appear together in these guidelines without distinguishing one from the other. Though the conventions and general guidelines apply to all settings, coding guidelines for outpatient and provider reporting of diagnoses will vary in a number of instances from those for inpatient diagnoses, recognizing that: The Uniform Hospital Discharge Data Set (UHDDS) definition of principal diagnosis does not apply to hospital-based outpatient services and provider-based office visits. Coding guidelines for inconclusive diagnoses (probable, suspected, rule out, etc.) were developed for inpatient reporting and do not apply to outpatients.

A. Selection of first-listed condition

In the outpatient setting, the term first-listed diagnosis is used in lieu of principal diagnosis. In determining the first-listed diagnosis the coding conventions of ICD-10-CM, as well as the general and disease specific guidelines take precedence over the outpatient guidelines. Diagnoses often are not established at the time of the initial encounter/visit. It may take two or more visits before the diagnosis is confirmed. The most critical rule involves beginning the search for the correct code assignment through the Alphabetic Index. Never begin searching initially in the Tabular List as this will lead to coding errors.

1. Outpatient Surgery

When a patient presents for outpatient surgery (same day surgery), code the reason for the surgery as the first-listed diagnosis (reason for the encounter), even if the surgery is not performed due to a contraindication.

2. Observation Stay

When a patient is admitted for observation for a medical condition, assign a code for the medical condition as the first-listed diagnosis. When a patient presents for outpatient surgery and develops complications requiring admission to observation, code the reason for the surgery as the first reported diagnosis (reason for the encounter), followed by codes for the complications as secondary diagnoses.

B. Codes from A00.0 through T88.9, Z00-Z99

The appropriate code(s) from A00.0 through T88.9, Z00-Z99 must be used to identify diagnoses, symptoms, conditions, problems, complaints, or other reason(s) for the encounter/visit.

C. Accurate reporting of ICD-10-CM diagnosis codes

For accurate reporting of ICD-10-CM diagnosis codes, the documentation should describe the patient's condition, using terminology which includes specific diagnoses as well as symptoms, problems, or reasons for the encounter. There are ICD-10-CM codes to describe all of these.

D. Codes that describe symptoms and signs

Codes that describe symptoms and signs, as opposed to diagnoses, are acceptable for reporting purposes when a diagnosis has not been established (confirmed) by the provider. Chapter 18 of ICD-10-CM, Symptoms, Signs, and Abnormal Clinical and Laboratory Findings Not Elsewhere Classified (codes R00-R99) contain many, but not all codes for symptoms.

E. Encounters for circumstances other than a disease or injury

ICD-10-CM provides codes to deal with encounters for circumstances other than a disease or injury. The Factors Influencing Health Status and Contact with Health Services codes (Z00-Z99) are provided to deal with occasions when circumstances other than a disease or injury are recorded as diagnosis or problems. See Section I.C.21. Factors influencing health status and contact with health services.

F. Level of Detail in Coding

1. ICD-10-CM codes with 3, 4, 5, 6 or 7 characters

ICD-10-CM is composed of codes with 3, 4, 5, 6 or 7 characters. Codes with three characters are included in ICD-10-CM as the heading of a category of codes that may be further subdivided by the use of fourth, fifth, sixth or seventh characters to provide greater specificity.

2. Use of full number of characters required for a code

A three-character code is to be used only if it is not further subdivided. A code is invalid if it has not been coded to the full number of characters required for that code, including the 7th character, if applicable.

G. ICD-10-CM code for the diagnosis, condition, problem, or other reason for encounter/visit

List first the ICD-10-CM code for the diagnosis, condition, problem, or other reason for encounter/visit shown in the medical record to be chiefly responsible for the services provided. List additional codes that describe any coexisting conditions. In some cases the first-listed diagnosis may be a symptom when a diagnosis has not been established (confirmed) by the physician.

H. Uncertain diagnosis

Do not code diagnoses documented as "probable", "suspected," "questionable," "rule out," or "working diagnosis" or other similar terms indicating uncertainty. Rather, code the condition(s) to the highest degree of certainty for that encounter/visit, such as symptoms, signs, abnormal test results, or other reason for the visit. Please note: This differs from the coding practices used by short-term, acute care, long-term care and psychiatric hospitals.

I. Chronic diseases

Chronic diseases treated on an ongoing basis may be coded and reported as many times as the patient receives treatment and care for the condition(s)

J. Code all documented conditions that coexist

Code all documented conditions that coexist at the time of the encounter/visit, and require or affect patient care treatment or management. Do not code conditions that were previously treated and no longer exist. However, history codes (categories Z80-Z87) may be used as secondary codes if the historical condition or family history has an impact on current care or influences treatment.

K. Patients receiving diagnostic services only

For patients receiving diagnostic services only during an encounter/visit, sequence first the diagnosis, condition, problem, or other reason for encounter/visit shown in the medical record to be chiefly responsible for the outpatient services provided during the encounter/visit. Codes for other diagnoses (e.g., chronic conditions) may be sequenced as additional diagnoses. For encounters for routine laboratory/radiology testing in the absence of any signs, symptoms, or associated diagnosis, assign Z01.89, Encounter for other specified special examinations. If routine testing is performed during the same encounter as a test to evaluate a sign, symptom, or diagnosis, it is appropriate to assign both the Z code and the code describing the reason for the non-routine test. For outpatient encounters for diagnostic tests that have been interpreted by a physician, and the final report is available at the time of coding, code any confirmed or definitive diagnosis(es) documented in the interpretation. Do not code related signs and symptoms as additional diagnoses. Please note: This differs from the coding practice in the hospital inpatient setting regarding abnormal findings on test results.

L. Patients receiving therapeutic services only

For patients receiving therapeutic services only during an encounter/visit, sequence first the diagnosis, condition, problem, or other reason for encounter/visit shown in the medical record to be chiefly responsible for the outpatient services provided during the encounter/visit. Codes for other diagnoses (e.g., chronic conditions) may be sequenced as additional diagnoses. The only exception to this rule is that when the primary reason for the admission/encounter is chemotherapy or radiation therapy, the appropriate Z code for the service is listed first, and the diagnosis or problem for which the service is being performed listed second.

M. Patients receiving preoperative evaluations only

For patients receiving preoperative evaluations only, sequence first a code from subcategory Z01.81, Encounter for pre-procedural examinations, to describe the pre-op consultations. Assign a code for the condition to describe the reason for the surgery as an additional diagnosis. Code also any findings related to the pre-op evaluation.

N. Ambulatory surgery

For ambulatory surgery, code the diagnosis for which the surgery was performed. If the postoperative diagnosis is known to be different from the preoperative diagnosis at the time the diagnosis is confirmed, select the postoperative diagnosis for coding, since it is the most definitive.

O. Routine outpatient prenatal visits

See Section I.C.15. Routine outpatient prenatal visits.

P. Encounters for general medical examinations with abnormal findings

The subcategories for encounters for general medical examinations, Z00.0-, provide codes for with and without abnormal findings. Should a general medical examination result in an abnormal finding, the code for general medical examination with abnormal finding should be assigned as the first-listed diagnosis. An examination with abnormal findings refers to a condition/diagnosis that is newly identified or a change in severity of a chronic condition (such as uncontrolled hypertension, or an acute exacerbation of chronic obstructive pulmonary disease) during a routine physical examination. A secondary code for the abnormal finding should also be coded.

Q. Encounters for routine health screenings

See Section I.C.21. Factors influencing health status and contact with health services, Screening