The D-dimer test is a foundational diagnostic tool used to assess a patient’s risk of dangerous blood clotting. This simple blood test measures a substance that circulates in the bloodstream, indicating active coagulation within the body. To ensure standardized documentation and billing, medical findings are classified using the International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) system. This system assigns specific codes to symptoms, injuries, and abnormal findings, including an elevated D-dimer result, which often triggers further medical investigation.
Understanding the D-Dimer Marker
D-dimer is a small protein fragment released into the bloodstream when a blood clot is broken down through a process called fibrinolysis. When a blood vessel is injured, the body activates proteins to form a stable clot, which is a mesh made of fibrin. This fibrin mesh is cross-linked to form a sturdy plug that stops the bleeding.
Once the injury is healed, the body dissolves the clot using the enzyme plasmin. Plasmin cuts the cross-linked fibrin into smaller pieces, and D-dimer is the smallest of these fragments. The presence of D-dimer indicates that a stable clot has both formed and subsequently been degraded.
A D-dimer test quantifies the level of this fragment in the blood, with normal concentrations typically falling below 0.5 milligrams per liter (mg/L). An elevated result means the level is above this range, signaling an abnormal or excessive amount of clot formation and breakdown. The test is highly sensitive, meaning a negative result is effective at ruling out certain clotting disorders, but it lacks specificity, as many non-clotting conditions can also cause an elevation.
Classifying the Elevated Finding
The specific ICD-10-CM code used to document an elevated D-dimer result is R79.1. This code is officially titled “Abnormal coagulation profile” and encompasses irregularities in the blood’s clotting ability, including D-dimer levels above the reference range. The ICD-10-CM system groups this code under a larger chapter dedicated to “Symptoms, signs and abnormal clinical and laboratory findings, not elsewhere classified.”
R79.1 is considered a finding code, not a final diagnosis code. This means it documents the objective laboratory abnormality detected in the patient’s blood work. The code is used when a specific cause for the abnormal D-dimer has not yet been determined or confirmed. If the elevated D-dimer leads to a confirmed diagnosis, such as a pulmonary embolism, the physician would then use the specific code for the embolism as the primary diagnosis. R79.1 functions as a temporary or secondary code to document the initial abnormal test result that triggered the subsequent diagnostic workup.
Clinical Significance of High D-Dimer Results
An elevated D-dimer result signals a potential underlying medical issue and prompts attention from healthcare providers. The test is most frequently used in the emergency setting to evaluate patients suspected of having a venous thromboembolism (VTE), which includes Deep Vein Thrombosis (DVT) and Pulmonary Embolism (PE). DVT is a blood clot, often in a leg vein, while PE occurs when a part of that clot breaks off and travels to the lungs, blocking a pulmonary artery.
These conditions cause D-dimer to rise because the body attempts to break down the newly formed clots. In patients with a low or intermediate likelihood of VTE, a normal D-dimer test can safely exclude the diagnosis, preventing the need for more invasive or costly imaging studies.
Beyond VTE, an elevated D-dimer can also be a marker for other serious conditions, notably Disseminated Intravascular Coagulation (DIC). DIC is a disorder where widespread activation of the clotting cascade leads to small clots forming throughout the body, which then rapidly consume clotting factors and platelets, paradoxically causing severe bleeding. The massive, simultaneous clot formation and breakdown in DIC results in extremely high D-dimer levels.
Other medical conditions can also elevate D-dimer levels, including recent surgery or trauma, infection, advanced age, cancer, liver disease, and normal pregnancy. Because of these many possible causes, an elevated D-dimer is an indication for further testing and clinical evaluation rather than a diagnosis in itself. Ultra-high D-dimer levels, sometimes exceeding 5,000 nanograms per milliliter, are often associated with severe underlying diseases like cancer or sepsis.