Does the Wound, Ostomy, and Continence Nurses (WOCN) society recommend Ankle-Brachial Index (ABI) tests for all lower extremity wounds?

ABI Testing for Lower Extremity Wounds: WOCN Recommendations

The WOCN Society does not recommend ABI testing for every lower extremity wound, but rather recommends it as part of a comprehensive vascular assessment for patients with suspected arterial disease or risk factors for PAD. 1

Indications for ABI Testing in Lower Extremity Wounds

• ABI testing is recommended as a first-line test for patients with suspected lower extremity PAD, defined as individuals with:

  • Exertional leg symptoms
  • Nonhealing wounds
  • Age ≥70 years
  • Age 50-69 years with a history of smoking or diabetes 2

• ABI should be performed in patients with history or physical examination findings suggestive of PAD to establish the diagnosis 2

• ABI measurement is reasonable in patients at increased risk of PAD even without history or physical examination findings suggestive of PAD 2

Limitations of ABI in Wound Assessment

• ABI may be normal in nearly one-quarter of patients with chronic limb-threatening ischemia, making it unreliable as the sole assessment tool 3

• The concordance between ABI and toe pressure/toe-brachial index among patients with chronic limb-threatening ischemia is poor, with only 58% of patients who meet criteria for abnormal toe pressures presenting with abnormal ABIs 3

• ABI may not be accurate when systolic blood pressure cannot be abolished by inflation of an air-filled blood pressure cuff (noncompressible pedal arteries), as occurs in some diabetic or elderly individuals 2

Comprehensive Vascular Assessment Approach

For optimal wound assessment, a more comprehensive approach is recommended:

1. Initial ABI measurement for all patients with lower extremity wounds 3

   • If ABI ≤0.90: PAD is confirmed, but additional testing is needed to assess wound healing potential
   • If ABI >1.40: Vessels are noncompressible, and TBI is mandatory

2. Additional testing when indicated:

   • Toe-brachial index (TBI) should be measured when ABI is >1.40 due to noncompressible vessels 2
   • In patients with normal (1.00-1.40) or borderline (0.91-0.99) ABI in the setting of nonhealing wounds, it is reasonable to diagnose CLI by using TBI with waveforms, TcPO2, or SPP 2

3. Perfusion assessment measures:

   • A TcPO2 >30 mm Hg or an SPP >40 mm Hg can predict wound healing potential 3, 4
   • These measures should be obtained in a warm room to prevent arterial vasoconstriction in response to cold 3

Clinical Impact of Early ABI Testing

• Early ABI testing (<30 days from wound identification) has been associated with:
  • Quicker time to vascular referral (13 days vs. 91 days)
  • Faster wound healing (117 days vs. 287 days)
  • Potentially lower amputation rates 5

Common Pitfalls to Avoid

• Relying solely on ABI may miss significant arterial disease in patients with diabetes or advanced age due to arterial calcification causing falsely elevated readings 3, 6

• Normal range ABI outcomes (0.9-1.4) cannot be taken to infer the absence of LEAD; ABI has a sensitivity of only 72.3% and specificity of 69.3% when using duplex ultrasound as a benchmark 6

• Failure to perform a pulse exam when a wound is identified may delay appropriate vascular assessment and intervention 5