An “uncertain diagnosis” refers to a condition documented by a clinician using terminology like “suspected,” “probable,” “likely,” “possible,” or “rule out.” Accurate coding of these conditions is important because it directly impacts hospital reimbursement, quality metrics, and the overall reliability of patient data. The ability to code an uncertain diagnosis depends entirely on the setting in which the patient is receiving care, with dramatically different rules applying to inpatient versus outpatient services.
Official Guidelines for Coding Uncertain Inpatient Diagnoses
For patients admitted to an acute care hospital as an inpatient, coding a suspected condition is definitively permitted, provided the documentation meets specific criteria. The official ICD-10-CM coding guidelines allow coders to assign a code for a condition documented as “probable,” “suspected,” “likely,” or “possible” as if the diagnosis were established. This rule applies to short-term acute, long-term care, and psychiatric hospitals.
This allowance is based on the rationale that the patient’s entire hospital stay, including the diagnostic workup and initial treatment, is driven by the suspicion of that condition. The resources expended in attempting to confirm or rule out the diagnosis justify coding it as present for facility billing purposes. For example, if a patient is admitted with a “possible pulmonary embolism” and receives aggressive anticoagulation therapy, the resources used reflect the treatment of an embolism.
For this rule to apply, the uncertain diagnosis must be documented in the patient’s record at the time of discharge or death. If the physician definitively documents that the condition has been “ruled out” before the patient leaves the facility, the condition cannot be coded. Terms such as “compatible with” and “consistent with” are also accepted indicators of uncertainty.
This guideline applies to both the Principal Diagnosis—the condition chiefly responsible for the patient’s admission—and any secondary diagnoses. Exceptions exist for certain infectious diseases where only confirmed cases can be coded, such as HIV infection, Zika virus, and, in some cases, COVID-19.
Critical Distinction: Outpatient Coding Rules
The rule allowing suspected diagnoses to be reported as confirmed is strictly limited to the inpatient setting and is forbidden in all other non-inpatient environments. This includes physician offices, hospital outpatient clinics, emergency department visits, ambulatory surgery centers, and observation stays. Compliance failure regarding this distinction is one of the most common coding errors.
In the outpatient setting, coders must adhere to a much stricter standard of documentation certainty. If a definitive diagnosis has not been established by the end of the encounter, the coder must not assign a code for a “probable,” “suspected,” or “rule out” condition.
Instead, the coder must report the signs, symptoms, or abnormal test results that prompted the visit or service. For instance, if a physician documents “probable appendicitis,” the coder would instead code the patient’s presenting symptoms, such as “abdominal pain” and “nausea.”
Provider Documentation Requirements and Coding Hierarchy
The ability to code an uncertain diagnosis in the inpatient setting places high reliance on the provider’s final documentation. The uncertain condition must be clearly stated in the discharge summary or the final progress note to justify code assignment. This confirms that the diagnostic uncertainty persisted throughout the patient’s stay.
The selection of the Principal Diagnosis follows a specific hierarchy, where the condition found to be the cause of admission is sequenced first. If multiple uncertain conditions are documented at discharge, the one chiefly responsible for the resources used is sequenced first.
Physician language is important; terms like “query” or “concern for” are often accepted as synonyms for uncertainty. However, a statement that a condition was “ruled out” means it must be excluded from the final codes.
If the documentation is ambiguous, such as a condition mentioned as “probable” early on but dropped from the final summary, a clinical documentation specialist must issue a physician query. This formal communication clarifies the final status of the diagnosis to ensure accurate code selection and compliance.