What is the ICD-10 code for a deranged Activated Partial Thromboplastin Time (APTT)?

ICD-10 Code for Deranged Activated Partial Thromboplastin Time (APTT)

The appropriate ICD-10 code for a deranged Activated Partial Thromboplastin Time (APTT) is R79.1 (Abnormal coagulation profile).

Understanding APTT and Its Clinical Significance

Activated Partial Thromboplastin Time (APTT) is a fundamental screening test used to evaluate the intrinsic and common pathways of the coagulation cascade. It is commonly used for:

• Screening for coagulation factor deficiencies
• Monitoring unfractionated heparin therapy
• Detecting the presence of lupus anticoagulant
• Evaluating unexplained bleeding tendencies

Common Causes of Deranged APTT

Medication-Related Causes

• Unfractionated Heparin (UFH) - most common medication cause with therapeutic range of 1.5-2.5 times control 1
• Direct Thrombin Inhibitors (e.g., dabigatran)
• Factor Xa inhibitors (though these may not reliably affect APTT)

Pathological Causes

• Lupus Anticoagulant - most common inhibitor causing prolonged APTT 1
• Factor deficiencies (particularly factors VIII, IX, XI, XII)
• Liver disease
• Disseminated intravascular coagulation (DIC)
• Vitamin K deficiency

Pre-analytical Factors

• Improper sample collection
• Presence of clots in the sample tube
• Incorrect blood-to-anticoagulant ratio

Coding Considerations

When coding for a deranged APTT:

1. Use R79.1 (Abnormal coagulation profile) as the primary code for an isolated abnormal APTT finding
2. If the cause is known, code for the underlying condition first, followed by R79.1
3. If the abnormal APTT is due to anticoagulant therapy, use:
   • Z79.01 for long-term use of anticoagulants
   • T45.515A for adverse effect of anticoagulants (if applicable)

Clinical Management Implications

The degree of APTT prolongation does not necessarily correlate with bleeding risk, and unnecessary fresh frozen plasma administration should be avoided for isolated APTT prolongation without bleeding or planned invasive procedures 1.

For patients requiring ongoing therapeutic anticoagulation with prolonged APTT:

• Consider switching to anti-Xa monitoring (target 0.3-0.6 IU/mL) instead of APTT 1
• Use INR for monitoring warfarin therapy, as it is not affected by baseline APTT prolongation 1

Documentation Tips

For proper coding, ensure documentation includes:

• The specific APTT value
• Whether it's an isolated finding or accompanied by other coagulation abnormalities
• Any known underlying cause
• Clinical context (e.g., anticoagulant therapy, bleeding symptoms)
• Any follow-up testing performed

Remember that identifying the cause of an abnormal APTT is more important than the degree of abnormality itself when assessing clinical risk 1.