Tobi Klein, CPC, RCC Jul 8, 2024 12:53:56 PM 10 min read

What Diagnosis Code Should I Report for Testing?


Utilizing testing codes when a definitive diagnosis is not available is essential to ensuring accurate coding, billing, and record-keeping. These codes facilitate the documentation of tests performed to investigate symptoms or rule out conditions. Testing codes help bridge the gap between symptom presentation and final diagnosis, thus supporting continuity of care and adherence to insurance requirements.

The Centers for Medicare and Medicaid Services (CMS) and the National Center for Health Statistics (NCHS) provide guidelines for coding and reporting using the International Classification of Diseases, 10th Revision, Clinical Modification (ICD-10-CM). These guidelines have been approved by the American Hospital Association (AHA), American Health Information Management Association (AHIMA), CMS, and NCHS and are the best resource for determining which code should be reported for testing.

First, it’s important to understand the significance of testing codes. Sign/symptom and “unspecified” codes have acceptable, even necessary, uses. While specific diagnosis codes should be reported when they are supported by the available medical record documentation and clinical knowledge of the patient’s health condition, there are instances when signs/symptoms or unspecified codes are the best choices for accurately reflecting the healthcare encounter.

Each healthcare encounter should be coded to the level of certainty known at the time of each encounter. As stated in the official coding guidelines, a joint effort between the healthcare provider and the coder is essential to achieve complete and accurate documentation, code assignment, and reporting of diagnoses and procedures. The importance of consistent, complete documentation in the medical record cannot be overemphasized. Without such documentation, accurate coding cannot be achieved. The entire record should be reviewed to determine the specific reason for the encounter and the conditions treated.

If a definitive diagnosis has not been established by the end of the encounter, it is appropriate to report codes for sign(s) and/or symptom(s) in lieu of a definitive diagnosis. When sufficient clinical information isn’t known or available about a particular health condition to assign a more specific code, it is acceptable to report the appropriate “unspecified” code (e.g., a diagnosis of pneumonia has been determined, but not the specific type). Unspecified codes should be reported when they are the codes that most accurately reflect what is known about the patient’s condition at the time of that particular encounter.

It would be inappropriate to select a specific code that is not supported by the medical record documentation or conduct medically unnecessary diagnostic testing in order to determine a more specific code.

Chapter 18 of the ICD-10-CM code book includes symptoms, signs, abnormal results of clinical or other investigative procedures, and ill-defined conditions regarding which no diagnosis classifiable elsewhere is recorded. Signs and symptoms that point to a specific diagnosis have been assigned to a category in other chapters of the classification.

Chapter 18 includes guidance on the following:

1. Use of Symptom Codes

Codes that describe symptoms and signs are acceptable for reporting purposes when a related definitive diagnosis has not been established (confirmed by the provider).

2. Use of Symptom Codes with a Definitive Diagnosis Code

Codes for signs and symptoms may be reported in addition to a related definitive diagnosis when the sign or symptom is not routinely associated with that diagnosis, such as the various signs and symptoms associated with complex syndromes. The definitive diagnosis code should be sequenced before the symptom code. Signs or symptoms that are associated routinely with a disease process should not be assigned as additional codes, unless otherwise instructed by the classification (e.g., Benign prostatic hyperplasia with lower urinary tract symptoms and nocturia).

3. Use of Combination Codes that Include Symptoms

ICD-10-CM contains a number of combination codes that identify both the definitive diagnosis and common symptoms of that diagnosis. When using one of these combination codes, an additional code should not be assigned for the symptom. (e.g., Cystitis with hematuria).

Here are a few examples of how to code testing after reviewing these ICD-10-CM guidelines:

A patient presents to the office with a cough and fever.  The provider documents the complaint and examines the patient. A flu test is performed in the office and the results are negative. The diagnosis code for the testing would be the signs and symptoms of cough and fever.

Many Electronic Medical Records systems require a diagnosis to be attached to the order for the testing. In this case, if the testing for the cough and fever had a positive result of influenza, this would be the appropriate diagnosis to document since the definitive diagnosis has been established at the time of the encounter.

A patient comes to the office with right knee pain, and the provider orders an x-ray. Since a definitive diagnosis has not been established yet, the provider gives the diagnosis of right knee pain on the order. The patient goes to the local hospital for testing and the radiologist documents osteoarthritis of the right knee in the impression and sends the report back to the provider.

When the patient comes back to the office to discuss the results and next steps, the provider will use the diagnosis code of osteoarthritis of the right knee, as now they have a definitive diagnosis.

A patient presents to the office with left flank pain, nausea and pain when urinating. Several tests are ordered: a CT scan of the abdomen and pelvis, a urinalysis in the office, and some laboratory testing. The provider tests the urine in the office and finds the patient has blood in his urine. The provider orders a CT scan and bloodwork for the flank pain and nausea to “rule out” kidney stones.

The encounter diagnosis will be flank pain, nausea and hematuria (this diagnosis was found at the time of the encounter and will also be attached to the urine testing). The diagnosis for “rule out” kidney stones cannot be used as a diagnosis on the outside testing; therefore, the flank pain and nausea will be added to the CT scan and the lab work orders as a definitive diagnosis has not been determined.

In conclusion, the strategic use of testing codes and “unspecified” codes when a diagnosis remains elusive is vital for maintaining the integrity of healthcare coding systems. These codes ensure that the provider’s investigative efforts are properly documented and reimbursed. By accurately capturing the diagnostic process, testing codes enhance the quality of patient care. As the healthcare landscape continues to grow, the importance of these codes will grow as well, thus increasing the importance of understanding of them.


Tobi Klein is a medical coder at Medic Management Group and is responsible for working with external clients and MMG revenue cycle management staff to ensure that provider claims are accurately submitted and appropriately reimbursed.