How to manage an elevated Partial Thromboplastin Time (PTT)?

Management of Elevated Partial Thromboplastin Time (PTT) of 57 Seconds

The first step in managing a PTT of 57 seconds is to determine the underlying cause, as this will guide appropriate management strategies. For patients requiring therapeutic anticoagulation with unfractionated heparin who have prolonged baseline PTT, anti-Xa monitoring should be used instead of PTT. 1

Diagnostic Approach

Initial Assessment

• Verify the result with repeat testing to rule out pre-analytical errors
• Check for clots in the sample tube and examine the blood smear to exclude false thrombocytopenia 2
• Order additional coagulation tests:
  • Prothrombin Time (PT)/INR
  • Fibrinogen
  • D-dimers or fibrin monomers 2
  • Platelet count

Common Causes of Elevated PTT

1. Anticoagulant Therapy

   • Unfractionated heparin (therapeutic PTT range: 1.5-2.5 times control, approximately 45-75 seconds) 2
   • Direct thrombin inhibitors

2. Pathological Conditions

   • Factor deficiencies (VIII, IX, XI, XII)
   • Lupus anticoagulant
   • Von Willebrand disease
   • Liver disease
   • Disseminated intravascular coagulation (DIC)

3. Pre-analytical Factors

   • Improper sample collection
   • Heparin contamination

Management Based on Cause

If Due to Heparin Therapy

If the patient is on therapeutic heparin:

• Determine if the PTT is within the target range (1.5-2.5 times control, approximately 50-70 seconds) 2
• For a PTT of 57 seconds, this is likely within therapeutic range for most institutions
• Continue monitoring according to institutional protocol:
  • Check PTT 6 hours after any dosage change
  • When two consecutive PTT values are therapeutic, measurements may be made every 24 hours 2
  • Monitor platelet count daily to detect heparin-induced thrombocytopenia 2

If the PTT is supratherapeutic (>75 seconds):

• Reduce heparin dose according to institutional nomogram
• For PTT >100 seconds, consider stopping infusion temporarily 1

If Heparin Resistance is Present

If the patient requires >35,000 units/day to achieve therapeutic PTT:

• Switch to anti-Xa monitoring (target 0.3-0.6 IU/mL) 1, 3
• This approach is safer and more effective than continuing to escalate heparin doses 3

If Due to Pathological Conditions

• Factor deficiencies:

  • Identify the specific factor deficiency through factor assays
  • Consider factor replacement therapy based on severity and clinical situation 1

• Lupus anticoagulant:

  • Perform confirmatory testing (mixing studies, dilute Russell's viper venom time)
  • No treatment needed for isolated PTT prolongation without bleeding 1
  • If anticoagulation is needed, use anti-Xa monitoring rather than PTT 1

• Liver disease:

  • Manage underlying liver condition
  • Fresh frozen plasma may be indicated if bleeding or before invasive procedures

Special Considerations

Concomitant Warfarin Therapy

• Be aware that warfarin markedly affects PTT; for each increase of 1.0 in INR, the PTT increases approximately 16 seconds 4
• The effects of warfarin and heparin on PTT are additive 4
• Do not reduce heparin dose based solely on elevated PTT if the patient is also on warfarin 4

Monitoring Options

• For patients with baseline prolonged PTT requiring heparin therapy, use anti-Xa levels (target 0.35-0.67 U/mL) instead of PTT 1, 3
• Weight-based heparin dosing (80 U/kg bolus followed by 18 U/kg/hour) achieves therapeutic levels faster than standard fixed dosing, but has higher risk of supratherapeutic levels 5

Common Pitfalls to Avoid

• Unnecessary FFP administration for isolated PTT prolongation without bleeding or planned invasive procedure, especially with Factor XII deficiency or lupus anticoagulant 1
• Relying on PTT for heparin monitoring in patients with baseline PTT prolongation 1
• Decreasing heparin dose in response to high PTT in patients on concomitant warfarin therapy, which can result in subtherapeutic heparin levels 4
• Ignoring clinical context when interpreting PTT values, as the same value may be therapeutic, subtherapeutic, or supratherapeutic depending on the clinical situation and institutional reference ranges

By following this systematic approach to evaluating and managing an elevated PTT of 57 seconds, clinicians can identify the underlying cause and implement appropriate management strategies to optimize patient outcomes.