How to Perform a Monofilament Test for Neuropathy

The monofilament test is a simple touch test. A thin nylon strand is pressed against the bare foot, and the person says whether they feel it. The result shows whether the feet can still sense enough to notice a blister, a cut, or a stone in a shoe before it turns into a wound. It checks only one kind of feeling, so a normal result does not mean the nerves are fully healthy.1Neuropad. A brief history of monofilament testing – Neuropad A version so simple that family members can do it at home with a fingertip has been shown to catch most at-risk feet.2PubMed. The Ipswich Touch Test: a simple and novel method to screen patients with diabetes at home for increased risk of foot ulceration

What the Monofilament Test Checks

The standard tool is a nylon filament, marked 5.07, that presses with about 10 grams of force when it bends into a C shape. That is why it is called the 10-gram monofilament.3WCEI. Diabetic Wound Care: Monofilament Testing Because the filament buckles at a set pressure, pushing harder does not raise the force the foot feels. So the test can compare one checkup with the next without depending on how hard the tester pushes. A filament that stays straight and stiff, or slips sideways, has not delivered the intended force, so that touch should not count. The test gives only a pass-or-fail answer at one pressure, not a measure of exactly how numb a spot is.

Not feeling the filament is called loss of protective sensation, meaning the foot can no longer feel pressure strong enough to warn of harm. It matters because nerve damage in the feet is common with long-standing diabetes. A foot that fails the test can be hurt without the person noticing, which raises the risk of ulcers.4iwgdguidelines.org. IWGDF Practical guidelines on the prevention and management of diabetic foot disease

The test checks only the larger nerve fibres that sense pressure, using numbness as a stand-in for nerve damage.5Neuropad. A brief history of monofilament testing – Neuropad It does not test temperature or pain feeling, which small nerve fibres carry. It does not check blood flow to the feet either, which is assessed separately by feeling pulses. Burning or tingling feet can still pass.

How to Prepare for the Test

The test should be done somewhere quiet and relaxed.6Canadian Journal of Diabetes. Appendix 12 – Diabetes Canada The person sits or lies down with shoes and socks off, since testing through socks or thin stockings gives no valid result.7blog.wcei.net. Monofilament, Testing Semmes Weinstein Cold feet straight from outside may feel less, so let them warm up first. The tester explains what will happen before starting.8blog.wcei.net. Monofilament, Testing Semmes Weinstein

Next comes a demonstration. Touch the filament to the hand, arm, elbow, or forehead first so the person knows what to expect.9Canadian Journal of Diabetes. Appendix 12 – Diabetes Canada The filament touch is light, and people may not know what they are waiting for. These spots usually have normal feeling, so the person learns what an ordinary touch is like and is less likely to guess. If their hands are numb too, the forehead or cheek is the better choice. Use the same filament and the same motion you will use on the foot, so the sensation matches.

Then ask them to say “yes” each time they feel the pressure on the foot.10blog.wcei.net. Monofilament, Testing Semmes Weinstein They close their eyes and keep their toes pointing up without moving.11blog.wcei.net. Monofilament, Testing Semmes Weinstein Avoid telling them which foot is next, too, because that lets them anticipate the touch.

How to Press the Filament Correctly

Hold the filament at a right angle to the skin.12Wounds Africa. MONOFILAMENT TEST Press just enough for it to bend into a C shape and hold for about one second.13Wounds Africa. MONOFILAMENT TEST The whole touch, approach, contact, and lift, takes about 1.5 seconds.14WCEI. Diabetic Wound Care: Monofilament Testing Do not press on ulcers, calluses, scars, or dead skin; test around their edge instead.15Health Resources & Services Administration. How to Use the LEAP Monofilament Calluses are thick and naturally numb, so testing on them can wrongly suggest nerve damage. Approach each spot slowly and smoothly, then lift straight away rather than dragging off. Keep the filament and your fingers clear of other parts of the foot as you approach, so an accidental touch does not cue the person.

Do not slide, brush, or tap. Sliding or brushing the filament across the skin adds a stroking feeling that is easier to sense, and tapping too quickly gives less time to notice the pressure.

Vary the timing so the person can’t guess. Leave irregular pauses between touches, and now and then pause without touching to see whether they still say yes.

If the person gives no answer at a spot, repeat the touch once there before recording it as missed. A single miss could reflect a lapse in attention or a poorly placed touch. Record only the touches not felt after the repeat.

Which Spots on the Foot to Test

Start with the toes, since they are easy to find, then move to the ball of the foot just behind them. Touch the arch and heel on healthy skin, away from thick, cracked, or callused areas, which are common at the heel.

Nerve damage from diabetes usually begins at the toes and spreads upward, so shorter versions work about as well. Quick checks often use only 3 or 4 spots per foot: under the big toe and the balls of the foot.20PubMed Central. Easier operation and similar power of 10 g monofilament test for screening diabetic peripheral neuropathy Testing just 4 spots per foot caught 90% of people found abnormal on a longer 16-spot check.21PubMed Central. Clinical Examination for the Detection of Protective Sensation in the Feet of Diabetic Patients In one comparison, 3 or 4 spots were about as accurate as 8 or 10.22PubMed Central. Comparison of the accuracy of monofilament testing at various points of feet in peripheral diabetic neuropathy screening

Test each foot fully, since one can be worse than the other. Mark each missed spot on a simple foot drawing. Keeping it lets you compare at the next checkup.

How to Read the Results

In one common method, failing to feel the filament at any tested spot counts as abnormal.23PubMed Central. Easier operation and similar power of 10 g monofilament test for screening diabetic peripheral neuropathy On a longer 18-spot check, missing 3 or more spots is taken as a true change in protective feeling.24PubMed Central. Diagnostic Accuracy of Monofilament Tests for Detecting Diabetic Peripheral Neuropathy: A Systematic Review and Meta-Analysis So the exact cutoff depends on how many spots your clinic tests.

Ask which method your clinic uses and what counts as abnormal there. Writing the result down with the date lets later tests show whether feeling is stable or getting worse.

After an abnormal result, the doctor usually adds other checks, such as a tuning fork test for vibration. Foot checks then become more frequent than yearly. You may be referred to a foot specialist and advised on footwear, and looking over your feet every day becomes essential.

A normal result means the foot can still feel firm pressure, not that the nerves are perfect. Burning or tingling should still be reported. Testing is repeated because feeling can fade over time.

How Accurate the Monofilament Test Is

In adults with diabetes, the test caught about 80% of people whose nerve damage showed on detailed nerve tests, and nearly everyone who failed it had nerve damage.25The Egyptian Journal of Neurology, Psychiatry and Neurosurgery. Semmes Weinstein monofilament test for detection of diabetic peripheral neuropathy: sensitivity and specificity Other studies found it caught only about 4 to 6 in 10 cases, depending on the spots used.26PubMed Central. Comparison of the accuracy of monofilament testing at various points of feet in peripheral diabetic neuropathy screening So passing the test does not rule out nerve damage.

A negative result can be wrong if the damage is early or affects other nerve fibres. Results also vary between clinics because different numbers of spots and different cutoffs change how many cases are caught, and because testers differ in how carefully they follow technique.

Using two tests together, such as the filament plus a tuning fork, catches more than 87% of nerve damage.27PubMed Central. Non-invasive assessment of vibration perception and protective sensation in people with diabetes mellitus: inter- and intra-rater reliability Current advice is to use more than one test as part of a wider foot exam.28PubMed Central. Non-invasive assessment of vibration perception and protective sensation in people with diabetes mellitus: inter- and intra-rater reliability A tuning fork checks vibration feeling, which can fade while light pressure is still felt. Both are quick and inexpensive.

Children are a special case. In children and teens with diabetes, the 10-gram filament caught fewer than 2 in 10 cases of nerve damage.29PubMed. Difficulties in screening for peripheral neuropathies in children with diabetes Finer filaments or vibration machines work better for them.30PubMed. Screening for peripheral neuropathies in children with diabetes: a systematic review

Why the Filament Itself Wears Out

Many filaments do not start at exactly 10 grams and can be off by up to 30%.31PubMed. Accuracy and durability of Semmes-Weinstein monofilaments: what is the useful service life? Force can drop by more than 10% over just 10 presses.32PubMed Central. Buckling Force Variability of Semmes–Weinstein Monofilaments in Successive Use Determined by Manual and Automated Operation Even a good filament stays in the usable 9 to 11 gram range for only about 7 to 9 days of clinic use, or 70 to 90 patients.33PubMed. Accuracy and durability of Semmes-Weinstein monofilaments: what is the useful service life? Repeated bending gradually softens the nylon so it buckles at a lower force, so let the filament rest between patients.

A worn filament presses lighter than intended, which can make a person with normal feeling miss spots and produce a false abnormal result. A filament that is too stiff does the reverse and could make someone with real loss of feeling look normal. Replace bent, kinked, or old filaments, and buy from a source that states the force and the 5.07 marking.

Checking Your Feet at Home With the Touch Test

You can check without a filament. In the Ipswich Touch Test, a helper lightly rests a fingertip for one to two seconds on the tips of the first, third and fifth toes of each foot, while the person, eyes closed, says when they feel it. With clear written instructions, family members doing it at home picked up about 78% of at-risk feet.34PubMed. The Ipswich Touch Test: a simple and novel method to screen patients with diabetes at home for increased risk of foot ulceration When the home test was normal, it was right about 93% of the time.35PubMed. The Ipswich Touch Test: a simple and novel method to screen patients with diabetes at home for increased risk of foot ulceration

To run it, sit the person comfortably with shoes and socks off and ask them to close their eyes. Rest your fingertip on the first toe, then the third, then the fifth, and repeat on the other foot. Touch lightly, with the pressure you would use resting a finger on an eyelid, and without pressing, poking, or stroking. Note any spot where they say nothing. Missing two or more of the six spots is a reason to call your clinic.

Home checks don’t replace clinic visits. Clinics also check pulses and look at skin and nails. Home testing is useful between visits to spot a change early, and looking at your feet daily for cuts and redness matters as much as touch testing.

How Often the Test Should Be Done

Even people with diabetes at very low foot risk should have the test once a year.36iwgdguidelines.org. IWGDF Practical guidelines on the prevention and management of diabetic foot disease The yearly check includes asking about past ulcers or amputations and feeling foot pulses.37iwgdguidelines.org. IWGDF Practical guidelines on the prevention and management of diabetic foot disease It is worth the effort because foot ulcers and amputations could fall by 25% to 40% with intensive prevention.38Diabetes In Control. Diabetic Foot Ulcers, Amputations Are Preventable

Ask for a check sooner if you notice new numbness, tingling, or burning in the feet, a blister or cut you didn’t feel happening, or changes in foot shape or new calluses. The test is also used for nerve damage from chemotherapy, so cancer patients can ask too.39PubMed. Evaluation of the Semmes-Weinstein filaments and a questionnaire to assess chemotherapy-induced peripheral neuropathy