R79.1
R79 — Other abnormal findings of blood chemistry
Chapter 18: Symptoms, Signs, and Abnormal Clinical and Laboratory Findings, Not Elsewhere Classified (R00-R99)
R70-R79 — Abnormal findings on examination of blood, without diagnosis
Clinical Definition
An abnormal coagulation profile refers to laboratory findings that indicate a disturbance in the blood clotting mechanism, detected through tests such as prothrombin time (PT), activated partial thromboplastin time (aPTT), international normalized ratio (INR), fibrinogen level, d-dimer, and thrombin time. These abnormalities may reflect an underlying coagulopathy, liver disease, medication effect (anticoagulant therapy), vitamin K deficiency, disseminated intravascular coagulation (DIC), or other conditions affecting the coagulation cascade. An elevated d-dimer — one of the most commonly encountered abnormal coagulation findings — is a fibrin degradation product that indicates recent or ongoing activation of the clotting and fibrinolytic systems, frequently evaluated in the workup for venous thromboembolism (VTE), pulmonary embolism (PE), and deep vein thrombosis (DVT).
ICD-10-CM code R79.1 is a pre-diagnosis finding code used when coagulation laboratory results are abnormal but the provider has not yet established a definitive underlying diagnosis. This code captures abnormal PT, aPTT, INR, fibrinogen, d-dimer, and other coagulation-related laboratory findings as a clinical observation. It should not be used when the abnormal result has been definitively linked to a specific coagulation disorder, which would be coded to the appropriate disease category (e.g., D68.x for coagulation defects, D65 for DIC, or I26.x for pulmonary embolism).
Clinical evaluation of an abnormal coagulation profile depends on which parameters are deranged. An isolated prolonged PT/INR suggests the extrinsic pathway or vitamin K-dependent factors, while a prolonged aPTT suggests intrinsic pathway factor deficiency or an inhibitor (such as lupus anticoagulant). An elevated d-dimer with clinical suspicion for VTE warrants imaging (CT angiography for PE, compression ultrasonography for DVT). Mixing studies, specific factor assays, and fibrinogen levels help narrow the differential diagnosis from a broad abnormal coagulation profile to a specific disorder.
When to Use R79.1
- ✓The provider documents an abnormal coagulation test result (PT, aPTT, INR, fibrinogen, d-dimer) without attributing it to a specific underlying coagulation disorder.
- ✓An elevated d-dimer is identified on laboratory evaluation and the patient is undergoing workup for possible VTE, PE, or DVT, but no definitive diagnosis has been established.
- ✓Pre-operative coagulation screening reveals an unexpected prolonged PT or aPTT that requires further evaluation before a specific diagnosis is reached.
- ✓The patient has abnormal INR results that are not attributed to anticoagulant therapy or a known liver disease, and the cause is under investigation.
- ✓Laboratory findings show an abnormal coagulation profile as an incidental finding during routine blood work or hospital admission panels, pending further diagnostic evaluation.
Common Coding Mistakes
- ⚠Using R79.1 when the abnormal coagulation is due to anticoagulant medication and is therapeutically expected — if the INR is elevated due to warfarin therapy, document the anticoagulant use with Z79.01 and any adverse effects with the appropriate T-code rather than R79.1.
- ⚠Using R79.1 when a specific coagulation disorder has been diagnosed — use D68.9 (coagulation defect, unspecified) or more specific D68.x codes when a coagulopathy has been identified, not the R79.1 finding code.
- ⚠Using R79.1 for confirmed DIC — use D65 (disseminated intravascular coagulation) when the provider has established this diagnosis.
- ⚠Using R79.1 for confirmed pulmonary embolism after elevated d-dimer — once PE or DVT is confirmed by imaging, use the appropriate I26.x or I82.x codes rather than the pre-diagnosis R79.1.
- ⚠Confusing R79.1 with R79.82 (elevated C-reactive protein) or R79.89 (other specified abnormal findings of blood chemistry) — R79.1 is specifically for coagulation-related abnormalities.
Related & Differential Codes
| Code | Description | Relationship |
|---|---|---|
| R79.82 | Elevated C-reactive protein (CRP) | Sibling |
| R79.89 | Other specified abnormal findings of blood chemistry | Sibling |
| R79.9 | Abnormal finding of blood chemistry, unspecified | Sibling |
| D68.9 | Coagulation defect, unspecified | Related |
| D68.4 | Acquired coagulation factor deficiency | Related |
| D65 | Disseminated intravascular coagulation (DIC) | Related |
| D68.51 | Activated protein C resistance (Factor V Leiden) | Related |
| D68.61 | Antiphospholipid syndrome | Related |
| I26.99 | Other pulmonary embolism without acute cor pulmonale | Related |
| I82.40 | Acute embolism and thrombosis of unspecified deep veins of lower extremity | Related |
| Z79.01 | Long-term (current) use of anticoagulants | Related |
| E56.1 | Vitamin K deficiency | Related |
Documentation Requirements
- 1Specific coagulation test results: document which tests are abnormal (PT, aPTT, INR, fibrinogen, d-dimer, thrombin time) and their measured values with reference ranges.
- 2Clinical context: document the reason for ordering coagulation studies (pre-operative screening, VTE workup, bleeding evaluation, incidental finding, medication monitoring).
- 3Current medications: document anticoagulant or antiplatelet therapy (warfarin, DOACs, heparin, aspirin) as these commonly affect coagulation parameters and may explain the abnormal results.
- 4Working diagnosis or differential: document whether the abnormal coagulation profile is suspected to be due to a specific etiology (liver disease, DIC, factor deficiency, medication effect) to guide code selection.
- 5Follow-up plan: document planned additional testing (mixing studies, specific factor assays, imaging for VTE) or referral to hematology for further evaluation.
- 6Liver function: document liver function test results if relevant, as hepatic dysfunction is a common cause of abnormal coagulation profiles.
Reimbursement & Billing Notes
ICD-10-CM code R79.1 is a valid, billable code accepted by Medicare, Medicaid, and commercial payers for encounters involving abnormal coagulation laboratory findings. It supports medical necessity for additional diagnostic workup including mixing studies, specific coagulation factor assays, d-dimer testing, thrombophilia panels, and imaging studies (CT pulmonary angiography, lower extremity venous duplex) when VTE is suspected based on an elevated d-dimer. R79.1 is appropriate for the initial encounter when the abnormal finding has been identified but a definitive diagnosis has not been established.
R79.1 does not map to a CMS-HCC risk adjustment category. Once a specific coagulation disorder is diagnosed (e.g., factor V Leiden, antiphospholipid syndrome, acquired coagulation factor deficiency), the definitive diagnosis code should replace R79.1 for subsequent encounters. Payers may question continued use of R79.1 across multiple encounters if additional workup should have led to a specific diagnosis. For encounters where the abnormal coagulation is solely due to therapeutic anticoagulation, Z79.01 (long-term use of anticoagulants) is more appropriate and does not imply a pathological finding.
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Try Free — No Credit Card RequiredFrequently Asked Questions
What is the ICD-10 code for elevated d-dimer?
The ICD-10-CM code for an elevated d-dimer, when no definitive diagnosis has been established, is R79.1 (abnormal coagulation profile). D-dimer is a coagulation-related laboratory test, and an abnormal result falls under the R79.1 category. Once a definitive diagnosis is made based on the elevated d-dimer (such as pulmonary embolism I26.x or DVT I82.x), the specific disease code should be used instead.
What is the ICD-10 code for abnormal INR?
An abnormal INR is coded as R79.1 (abnormal coagulation profile) when the abnormal result is a pre-diagnosis finding under investigation. If the abnormal INR is due to anticoagulant therapy (e.g., warfarin), the appropriate code depends on the clinical context — Z79.01 (long-term use of anticoagulants) for expected therapeutic effect, or T45.515A (adverse effect of anticoagulants, initial encounter) if the INR is supratherapeutic and clinically significant.
When should R79.1 be replaced with a more specific code?
R79.1 should be replaced with a more specific diagnosis code as soon as the underlying cause of the abnormal coagulation profile is identified. For example, if workup reveals factor V Leiden, use D68.51; if DIC is diagnosed, use D65; if pulmonary embolism is confirmed, use I26.x. R79.1 is intended as a pre-diagnosis finding code and should not persist as the sole diagnosis once a definitive etiology has been established.
Can R79.1 be used for abnormal PT or aPTT?
Yes, R79.1 (abnormal coagulation profile) covers abnormal findings across all standard coagulation tests, including prothrombin time (PT), activated partial thromboplastin time (aPTT), INR, fibrinogen, d-dimer, and thrombin time. It is the appropriate pre-diagnosis code when any of these coagulation parameters are abnormal and the cause has not yet been determined.
What is the ICD-10 code for d-dimer test?
R79.1 is the ICD-10-CM diagnosis code that supports ordering a d-dimer test when there is clinical suspicion for abnormal coagulation. The CPT code for the d-dimer laboratory test itself is 85379 (D-dimer; quantitative). Use R79.1 as the diagnosis code when reporting the result of an abnormal d-dimer, or use the clinical indication code (e.g., R06.02 for dyspnea, R07.9 for chest pain) when ordering the test for suspected PE/DVT.
Is R79.1 appropriate for a patient on blood thinners with expected lab changes?
No. If the abnormal coagulation results are an expected consequence of anticoagulant therapy, R79.1 should not be used. Instead, code Z79.01 (long-term use of anticoagulants) to document the medication use. R79.1 is reserved for unexpected or unexplained abnormal coagulation findings that require further evaluation. If a patient on anticoagulants has a supratherapeutic INR causing adverse effects, use the appropriate T-code for adverse effects of anticoagulants.
What is the difference between R79.1 and D68.9?
R79.1 (abnormal coagulation profile) is a finding code used when coagulation test results are abnormal but no specific coagulation disorder has been diagnosed. D68.9 (coagulation defect, unspecified) is a disease code used when the provider has diagnosed a coagulation defect or coagulopathy, but the specific type has not been determined. R79.1 represents an abnormal lab result; D68.9 represents a diagnosed condition. Use R79.1 during initial workup and D68.9 when a coagulopathy has been confirmed.