Tests
1st tests to order
clinical diagnosis
Test
The diagnosis of diabetes-related foot disease is based primarily on a thorough, structured clinical examination, which should be performed in all patients with newly diagnosed diabetes. Examination should be repeated lifelong at regular intervals, as determined by risk stratification systems, guidelines and local screening protocols.[24][40]
Result
may show ulcers or pre-ulcerative skin lesions, bone or joint deformities, impaired sensation or proprioception, weak or absent pulses, and/or signs of infection, inflammation or ischemia
Tests to consider
CBC
Test
Ordered in all patients with suspected diabetic foot infection as part of IWGDF/IDSA system for classifying infection severity. WBC count correlates poorly with infection severity.[44]
Result
may show leukocytosis
blood glucose level
Test
Ordered in all patients with suspected diabetic foot infection. Often elevated in the presence of infection.
Result
may be elevated
CRP
erythrocyte sedimentation rate
renal function
Test
Can be helpful in determining the feasibility of giving iodinated contrast for arterial imaging (if necessary).
Result
variable
microbiologic culture
Test
If a diabetic foot infection is suspected, a tissue specimen should be collected from the base of the wound via curettage or biopsy and sent for culture.[44] Although more burdensome to collect, tissue specimens provide culture results with higher specificity and sensitivity than superficial swabs.[44]
In low-resource settings, a Gram-stain smear may be used as an alternative to culture to visualize the class of causative pathogen.[44] Do not take samples for culture if the wound is not clinically infected. False positive culture results may lead to the unnecessary prescription of antibiotics, which could cause harmful side effects and promote antibiotic resistance.[50]
Result
positive for causative organism in infection, sensitivities may guide antibiotic treatment
x-ray foot
Test
Perform if the clinical exam is suggestive of any bone or joint deformities, fractures, osteomyelitis, or Charcot neuro-osteoarthropathy.[44][51] Weight-bearing films should be considered whenever feasible, especially in patients with Charcot neuro-osteoarthropathy.[9][33]
Result
may show hypolucencies, cortical destruction/osteolysis, and/or joint subluxation
ankle/toe pressures and brachial indices
Test
Should be ordered in patients with a diabetic foot ulcer and a history and exam suggestive of peripheral arterial disease (PAD), particularly when the physical exam finds absent or weak pulses, or is limited by edema. Ankle pressures may be spuriously elevated because of arterial calcification and thus should be augmented by toe systolic pressures.[24]
Joint guidelines from the International Working Group on the Diabetic Foot, European Society for Vascular Surgery and Society for Vascular Surgery note that no single test has been found to reliably exclude PAD in patients with a diabetic foot ulcer or gangrene. The guidelines recommend evaluation of pedal Doppler waveforms in combination with ankle-brachial index (ABI) and toe-brachial index (TBI).[11]
Result
toe systolic pressures <30 mmHg are suggestive of PAD and poor ulcer healing. ABI reduced if PAD present; PAD is less likely if ABI is 0.9 to 1.3, TBI is ≥0.70, and triphasic or biphasic pedal Doppler waveforms are present
pedal doppler waveforms with pulse volume recordings (PVR)
Test
Performed in patients with suspected peripheral arterial disease (PAD).[11][24] Evaluation of the arterial pressure waveform using pulse volume recording via pneumoplethysmography can add valuable information to the isolated ankle-brachial index (ABI), particularly if the ABI is falsely elevated.
Joint guidelines from the International Working Group on the Diabetic Foot, European Society for Vascular Surgery and Society for Vascular Surgery note that no single test has been found to reliably exclude PAD in patients with a diabetic foot ulcer or gangrene. The guidelines recommend evaluation of pedal Doppler waveforms in combination with ABI and toe-brachial index (TBI).[11]
Result
any qualitative sequential decrease in pulsatility of the waveform suggests PAD; PAD is less likely if ABI is 0.9 to 1.3, TBI is ≥0.70, and triphasic or biphasic pedal Doppler waveforms are present
duplex ultrasound
Test
Consider in patients with diabetes, peripheral arterial disease and a foot ulcer or gangrene, for whom revascularization is being considered.[11]
The most widely used modality to assess location and degree of stenosis as well as patency of bypass grafts.[53]
Result
peak systolic velocity ratio >2.0 = stenosis >50%
catheter digital subtraction angiography (DSA)
Test
Consider in patients with diabetes, peripheral arterial disease and a foot ulcer or gangrene, for whom revascularization is being considered.[11]
DSA is the preferred imaging technique, particularly for arteries below the knee and foot, but is an invasive procedure and not as widely available as other modalities. Often used when CT or MR angiography are unavailable, fail to clearly define the anatomy, or when endovascular intervention is planned.[11]
Result
depiction of the foot arterial tree and accurate detection of hemodynamically significant (i.e., >50%) stenosis or occlusions between the aorta and the foot (if peripheral artery disease present)
CT angiography
Test
Consider in patients with diabetes, peripheral arterial disease (PAD) and a foot ulcer or gangrene, for whom revascularization is being considered.[11]
Poorer diagnostic accuracy compared with catheter angiography due to the perigeniculate/infrageniculate distribution of atherosclerotic lesions common in patients with diabetes mellitus and foot ulcers (because of inferior spatial resolution) and vessel wall calcification.
Result
depiction of the foot arterial tree and accurate detection of hemodynamically significant (i.e., >50%) stenosis or occlusions between the aorta and the foot (if PAD present)
MR angiography
Test
Consider in patients with diabetes, peripheral arterial disease (PAD) and a foot ulcer or gangrene, for whom revascularization is being considered.[11]
Images cannot define the extent of calcification, which may impact revascularization strategies.
Result
depiction of the foot arterial tree and accurate detection of hemodynamically significant (i.e., >50%) stenosis or occlusions between the aorta and the foot (if PAD present)
MRI foot
Test
Should be performed (with and/or without intravenous contrast) if initial x-ray is negative or indeterminate but clinical suspicion of osteomyelitis remains, or to differentiate from noninfectious structural changes related to Charcot neuro-osteoarthropathy.[33][51]
Where initial x-ray is positive for osteomyelitis, MRI is also recommended to aid treatment planning.[51]
Result
hypointense areas of bone on T1 sequences; hyperintense areas of bone on T2 sequences; soft-tissue fluid collections (if osteomyelitis present)
CT foot
Test
An alternative to MRI for diagnosing diabetes-related osteomyelitis of the foot, if MRI is contraindicated.[51]
Result
may show findings of acute osteomyelitis (periosteal reaction, endosteal scalloping, osseous destruction) or chronic osteomyelitis (sequestrum, involucrum, cloaca, and sinus tracts)
18F-fluorodeoxyglucose (FDG)-PET/CT
Test
An alternative to MRI for diagnosing diabetes-related osteomyelitis of the foot, if MRI is contraindicated.[44]
Result
may support a diagnosis of osteomyelitis
99mTc-exametazime hexa methyl propylene amine oxime (HMPAO)-labeled white blood cell scintigraphy
Test
An alternative to MRI for diagnosing diabetes-related osteomyelitis of the foot, if MRI is contraindicated.[44]
Result
may support a diagnosis of osteomyelitis
99mTc-labeled ubiquicidin (UBI) SPECT/CT single photon emission computed tomography (SPECT/CT)
Test
An alternative to MRI for diagnosing diabetes-related osteomyelitis of the foot, if MRI is contraindicated.[44]
Result
may support a diagnosis of osteomyelitis
Emerging tests
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