Monofilament Test Interpretation
The monofilament test is interpreted as normal (protective sensation present) when the patient correctly identifies 2 out of 3 applications at each tested site; abnormal results (fewer than 2 out of 3 correct) indicate loss of protective sensation (LOPS) and identify patients at risk for diabetic foot ulceration. 1, 2
Test Interpretation Criteria
Normal Result (Protective Sensation Present)
- Protective sensation is present when the patient correctly answers 2 out of 3 applications at each tested site. 1, 2
- This indicates the absence of clinically significant distal sensorimotor polyneuropathy affecting protective sensation at the time of testing. 2, 3
- The patient does not have LOPS, which is the primary risk factor for diabetic foot ulceration that monofilament testing is designed to detect. 3
Abnormal Result (Loss of Protective Sensation)
- An abnormal result occurs when the patient has 2 out of 3 incorrect answers at any tested site, indicating the patient is at risk for ulceration. 1, 2
- This represents loss of protective sensation and confirms the presence of distal sensorimotor polyneuropathy. 2, 4
- Research demonstrates that inability to feel the 5.07 (10-g) monofilament represents a sensory threshold more than 50 times greater than normal, meaning roughly 98% of sensory ability has been lost. 5
Critical Testing Technique Requirements
The validity of your interpretation depends entirely on proper technique:
- The test must be performed with the patient unable to see where or whether the monofilament is applied. 1, 2
- Apply the monofilament perpendicular to the skin with sufficient force to cause buckling for approximately 2 seconds total. 1, 2
- Each site requires three questions: two actual applications plus one mock application where no filament is applied. 1, 2
- Test three standardized sites on each foot (typically plantar surface of first toe, third metatarsal head, and fifth metatarsal head). 2
- Avoid testing directly on calluses, scars, ulcers, or necrotic tissue. 1, 2
Management Based on Results
If Normal (Protective Sensation Intact)
Continue annual monofilament screening as recommended by the American Diabetes Association to identify future development of neuropathy. 3, 4
Patient education should include:
- Daily foot inspection and proper nail care. 3
- Never walk barefoot, in socks only, or in thin-soled slippers. 3
- Maintain optimal glycemic control to prevent future neuropathy development. 3
Level 1 care is appropriate (general practitioner, podiatrist, diabetic nurse) as the patient does not have high-risk features requiring specialized multidisciplinary foot care. 3
If Abnormal (Loss of Protective Sensation)
The patient requires risk stratification and escalation of care:
- Patients with LOPS are at significant risk for diabetic foot ulceration and require more intensive monitoring. 2, 4
- Consider referral to Level 2 care (diabetologist, surgeon, vascular surgeon, podiatrist, diabetic nurse, in collaboration with shoe-maker/orthotist) or Level 3 specialized multidisciplinary diabetic foot care center depending on additional risk factors. 1
- Implement comprehensive foot protection strategies including therapeutic footwear and more frequent foot examinations. 3
Important Clinical Caveats
The monofilament test only assesses large fiber function and protective sensation; it does not evaluate small fiber neuropathy (pain, temperature sensation). 2, 3 Patients may have small fiber neuropathy even with normal monofilament testing. 2, 3
Monofilaments lose their buckling force with extended use, which affects test reliability—replace monofilaments regularly to maintain accuracy. 1, 3, 4
Testing 3-4 sites per foot is as effective as testing 8-10 sites for screening purposes, so the standard three-site protocol is sufficient and more time-efficient. 6, 7
Combine monofilament testing with vibration testing (128-Hz tuning fork) for comprehensive neuropathy assessment, though combining tests does not significantly add value beyond individual screening tests. 4, 8