Most Critical Test: 10-g Monofilament Test
The monofilament test (Option B) is the most critical test to perform because this patient's clinical presentation—numbness, inability to perceive touch and sensation, and a non-healing ulcer—strongly suggests loss of protective sensation (LOPS), which is present in 78% of diabetic patients with foot ulcers, and the monofilament test is explicitly designed to diagnose LOPS. 1
Why Monofilament Testing is the Priority
The American Diabetes Association explicitly states that neurological examination of the diabetic foot is designed to identify LOPS rather than early neuropathy, making the 10-g monofilament test the primary diagnostic tool for this exact clinical scenario. 1 The patient's complaint of numbness and inability to perceive touch and sensation are classic symptoms requiring objective confirmation through monofilament testing. 1
Diagnostic Significance
- The monofilament test is the single most useful and sensitive test for diagnosing LOPS and identifying feet at risk for ulceration. 1
- Loss of protective sensation is the single most common component cause for diabetic foot ulceration, present in 78% of cases. 1
- The test should be performed with at least one other neurological assessment (pinprick, temperature, vibration with 128-Hz tuning fork, or ankle reflexes) to confirm the diagnosis. 2, 1
- Absent monofilament sensation confirms LOPS, while at least two normal tests (with no abnormal test) rules it out. 1
Impact on Management
Confirming LOPS through monofilament testing fundamentally changes the entire management approach: 1
- Requires prescription of specialized therapeutic footwear 2, 1
- Mandates more frequent monitoring (every 1-3 months rather than annually) 3
- Necessitates immediate referral to foot care specialists for ongoing preventive care and lifelong surveillance 2, 1
- Triggers patient education on daily foot inspection and never walking barefoot 3
Why Not the Other Options
ABI Testing (Option A)
- ABI is indicated for evaluating peripheral arterial disease (PAD), not for diagnosing the underlying cause of a neuropathic ulcer. 1
- The American Diabetes Association recommends ABI only when initial screening reveals symptoms or signs of PAD (leg fatigue, claudication, rest pain, decreased/absent pedal pulses). 2, 4
- This patient has no mention of vascular symptoms or absent pulses—the presentation is purely neuropathic. 2
Pressure Point Assessment (Option C)
- Pressure assessment becomes relevant after confirming LOPS through monofilament testing, as part of the treatment strategy involving therapeutic footwear and offloading. 1
- It is not a diagnostic test but rather a component of management planning once neuropathy is established. 1
Critical Clinical Pitfall
Do not assume neuropathy based solely on history—objective confirmation with monofilament testing is essential for proper risk stratification and management planning. 1 The patient's subjective complaint of numbness requires objective documentation through standardized testing to justify the intensive interventions required for LOPS. 1