Why WEST™
1. Von Frey used horse hairs to measure tactile sensitivity. Many years later, Dr. Sidney Weinstein used nylon monofilaments. Nylon is more consistent. Judy Bell-Krotoski lauded Dr. Weinstein’s set of 20 graduated-force monofilaments, the Semmes Weinstein Monofilaments. Each monofilament achieved its force by a variation in width, keeping length constant. Nevertheless, individual calibration of the Semmes Weinstein Monofilaments was deemed appropriate by Dr. Weinstein.
2. Many years later, Drs. Weinstein and Drozdenko with Mr. C. Weinstein created the Weinstein Enhanced Sensory Test TM (WEST™ ). The WEST™ mimicked thresholds of the Semmes Weinstein (and subsets of the S-W) in neuropathic-free individuals. For those with common neuropathies (large-axonal damage), however, the thresholds from the WEST were more sensitive to damage (higher). Was the WEST’s advantage that it was calibrated – each monofilament applied the anticipated force? Yes, but other patented improvements were achieved. These improvements include a long life, and the instrument’s sensitivity to, for example, diabetic nerve damage.
3. Several models have derived from the WEST: WEST-hand™, WEST-foot™, and WEST-D™ are all five-monofilament (Softip™ ) instruments. They each present a different set of forces. Let me explain. Hand therapists decided that loss of protective sensation comes when the patient no longer detects 4 g. Diabetologists or podiatrists, however, use 10 g. The different models reflect user needs.
4. For foot-screening purposes, the CT-Bio™ folding monofilament may hold a Softip or common tipped 10-g monofilament.
5. The five-Softip monofilament esthesiometers (nerve testers) may be used with the Rapid Threshold Procedure to achieve one of ten outcomes quickly. This, the five monofilaments (used with the RTP) gives the tester the power of ten monofilaments (used with ordinary procedures). Alternatively, instead of the RTP, one can use a procedure to test for malingerers.
WEST-hand™ Terse Manual in English
Copyright 2007
General Information
1. The lengths of the filaments may be different.
2. Filaments may not be parallel to one another or may have a slight bend.
3. If a filament has a sharp bend, return for recalibration.
4. You may rotate several filaments for faster testing, but please store the instrument with all the filament pointing in the same general direction.
5. If a filament becomes stuck, rotate it in the opposite direction.
Method to obtain sensation levels
Rapid Threshold Procedure
Use a descending threshold procedure (e.g., start at 4 g). Use catch trails (act as if you are stimulating, but don't). Make sure that the patient cannot solve the tactile sensory task using visual information. We enclose a clicker because indicating the interval of potential stimulation helps the patient solve the detection task and eases creation of catch trials. Threshold is not solely determined by the first failure to detect. At the first failure to detect, stimulate with the next more forceful filament. At this point, either the person detects or not. If not, this level is threshold. (The patient has just detected and failed to detect this level.) If detects, proceed to the missed detection level (i.e., one filament lower in force) and stimulate. At this point, either the person detects or not. If not, the threshold is taken as half way between the last twice-detected filament and this twice-missed filament. (The more forceful filament was detected twice, and the less forceful filament was missed twice.) Note, in this case threshold does not correspond to a filament value, but to a value between filaments. If detects, then proceed as if the patient never missed (looking for a new first failure to detect). The Rapid Threshold Procedure works if the patient does not give false positive responses to the catch trails. In experience, it works even if the patient initially gives false positive responses. Otherwise, use some other procedure, for example, The Carpal Tunnel Test TM.
Dos and Don'ts
- Avoid touching the stalks of the filaments, which may affect calibration.
- Excessive heat affects calibration. Keeps filaments off window sills and away from fire.
- Never test open wounds, eyes, mucous membranes, oral cavity or damaged skin.
- Larger forces (>0.2 g) may damage newly grafted, transplanted or fragile skin.
- The contacting filament tips should be disinfected between patients.
- The tips and stalks are nylon. Anything that affects nylon is contraindicated.
- Do not place the stalks into a disinfecting solution; just the contacting tips.
Carpal Tunnel Test
Curt Weinstein, M.A., & Sidney Weinstein, Ph.D.
Copyright 1996, 2000, 2001, 2002
1. Rationale
Sensory-nerve damage is often both detected and classified by the loss of tactile sensation. Loss of tactile sensation is usually estimated by determining an absolute threshold, i.e., the smallest force reliably detectable. A potential confound has been found for patients with the job classification of physical laborer. Even before they become patients, scientific evaluations show that they have increased thresholds, and, thus, it is difficult to detect mild or early-onset of nerve damage accurately in this population using an absolute threshold. In patients with repetitive motion syndromes, such as Carpal Tunnel Syndrome (CTS), loss of tactile sensation due to nerve injury may be correlated with loss of tactile sensation due to protective skin thickening (including callus). This correlation does not present a problem for the evaluation of severe cases of CTS. For the detection of early-developing CTS, however, the correlation creates a problem in detection. Good estimates of the smallest detectable force are not sufficient to differentiate between impaired nerves and affected skin in cases of first emerging CTS. Thus, the discovery of a minimally elevated threshold will not reveal whether the nerves are compromised or whether the skin was thickened. An alternative procedure, fortunately, can be used to test for sensory deficit, even in the presence of callus. 1 This alternative procedure tests the ability of the patient to differentiate between easily detectable stimuli, i.e., super-threshold forces. The confounding effect of skin thickening affects the evaluation of threshold-level forces to a much greater extent than these super-threshold forces. To evaluate CTS, this procedure measures the patient's ability to differentiate between two super-threshold forces. This procedure may also detect malingerers, patients who deliberately try to confound the test by lying.
2. Overview
The test requires twenty trials. Each trial consists of the application of two different forces in close temporal proximity and with a randomized order of presentation. The patient's task is to report which of the two stimuli feels heavier. Each stimulus is applied for one full second, with a half second interval of separation. Therefore, each trial takes about 2.5 seconds for the tester to administer and about three additional seconds for the patient to respond either "first" or "second." The twenty trials take less than two minutes. For the test to be scored correctly, patients must indicate a preference, even if they only guess. 2 Unaffected patients should score a perfect 20 correct. When the patient is totally anesthetic, the statistically expected score is ten correct responses. Therefore, scores statistically lower than ten (e.g., less than six) indicate at least one of the following: (1)†the patient is malingering or (2)†the instructions are misunderstood or (3)†a very infrequent event has occurred.
3. Detailed Procedures
3.1 Choose one of the four CTS Test Forms below. Each form presents a particular 20-item random sequence of paired trials -- 2 vs. 4 g. The patient compares the two stimuli twenty times. The score is the number of correct trials. Scores less than twenty reflect neuropathy. Scores less than six reflect additional concerns (see section 4.).
3.2 Instructions to patient: I will be touching you in succession with two differently weighed probes. Your job is to tell me which probe feels heavier--the first or the second. So you know when the touches should occur, surrounding each touch will be a click. This is what you should experience: hear a click, feel touch number one, hear a click, and then hear a click, feel touch number two, hear a click. After the fourth click, tell me whether the first or second touch was heavier. If you are unsure, please guess. There is no penalty for guessing; do the best you can. We will be repeating the procedure several times. Any questions?
3.3 Instruction to tester: The patient's view of the testing site should be blocked. Apply the first filament (2 or 4 g) to the base of the thumb (or the site of sensory complaint) for a full second. Just before you slowly bend the filament onto the skin, press the clicker to cue the patient of the start of the stimulus interval. Then silently say "one Mississippi" to approximate a one-second application, and then slowly lift the filament from the skin. Release the clicker to cue the patient of the end of the first interval. Wait about half a second and apply the second filament (4 or 2 g) in the same slow, deliberate manner, cueing the patient with the clicker. Prompt the patient for a response, only if necessary. The patient should catch on and respond after the second click of the second stimulus. Record all responses on the testing form. After the twentieth response from the patient, tell the patient that the test is complete. Count the number of correct trials, and record that count next to "Total."
4. Expected Results.
We believe that most people without neuropathy and without heavy callus at the site of testing will score 20. A greater sensory deficit scores lower--to a point. Certainly scores from 19 to 10 suggest an increasingly greater deficit. Statistically speaking, however, patients void of tactile sensation will have a mean score of 10 with a standard deviation of about 2.2. Patients with greater tactile sensation will have higher scores with smaller standard deviations. Scores statistically lower than ten (e.g., less than six) indicate that the patient may be malingering. Other valid interpretations to a low score include: the instructions may have been be misunderstood, or a rare event occurred by chance in a person with diminished tactile sensibility. As necessary, you may retest the patient, using another test form, to obtain a better index of sensibility (average the two scores, unless you suspect that the patient had misunderstood the original instructions).
Four random testing orders (forms) are encoded on one test sheet. Please contact us to request the Test Form.
The 50 vs. 10 Test
Curt Weinstein
Copyright 2007
1. Rationale
To evaluate sensibility, this procedure measures the patient's ability to differentiate between two super-threshold forces. This procedure may also detect malingerers, patients who deliberately try to confound the test by lying.
2. Overview
The test requires twenty trials. Each trial consists of the application of two different forces in close temporal proximity and with a randomized order of presentation. The patient's task is to report which of the two stimuli feels heavier. Each stimulus is applied for one full second, with a half second interval of separation. Therefore, each trial takes about 2.5 seconds for the tester to administer and about three additional seconds for the patient to respond either "first" or "second." The twenty trials take less than two minutes. For the test to be scored correctly, patients must indicate a preference, even if they only guess. 1 Unaffected patients should score a perfect 20 correct. When the patient is totally anesthetic, the statistically expected score is ten correct responses. Therefore, scores statistically lower than ten (e.g., less than six) indicate at least one of the following: (1)†the patient is malingering or (2)†the instructions are misunderstood or (3)†a very infrequent event has occurred.
3. Detailed Procedures
3.1 Choose one of the four CTS Test Forms below. Each form presents a particular 20-item random sequence of paired trials--10 vs. 50 g. The patient compares the two stimuli twenty times. The score is the number of correct trials. Scores less than twenty reflect neuropathy. Scores less than six reflect additional concerns (see section 4.).
3.2 Instructions to patient: I will be touching you in succession with two differently weighed probes. Your job is to tell me which probe feels heavier--the first or the second. So you know when the touches should occur, surrounding each touch will be a click. This is what you should experience: hear a click, feel touch number one, hear a click, and then hear a click, feel touch number two, hear a click. After the fourth click, tell me whether the first or second touch was heavier. If you are unsure, please guess. There is no penalty for guessing; do the best you can. We will be repeating the procedure several times. Any questions?
3.3 Instruction to tester: The patient's view of the testing site should be blocked. Apply the first filament (10 or 50 g) to the inner side of the great toe (or the site of sensory complaint) for a full second. Just before you slowly bend the filament onto the skin, press the clicker to cue the patient of the start of the stimulus interval. Then silently say "one Mississippi" to approximate a one-second application, and then slowly lift the filament from the skin. Release the clicker to cue the patient of the end of the first interval. Wait about half a second and apply the second filament (50 or 10 g) in the same slow, deliberate manner, cueing the patient with the clicker. Prompt the patient for a response, only if necessary. The patient should catch on and respond after the second click of the second stimulus. Record all responses on the testing form. After the twentieth response from the patient, tell the patient that the test is complete. Count the number of correct trials, and record that count next to "Total ."
4. Expected Results.
We believe that most people without neuropathy and without heavy callus at the site of testing will score 20. A greater sensory deficit scores lower--to a point. Certainly scores from 19 to 10 suggest an increasingly greater deficit. Statistically speaking, however, patients void of tactile sensation will have a mean score of 10 with a standard deviation of about 2.2. Patients with greater tactile sensation will have higher scores with smaller standard deviations. Scores statistically lower than ten (e.g., less than six) indicate that the patient may be malingering. Other valid interpretations to a low score include: the instructions may have been be misunderstood, or a rare event occurred by chance in a person with diminished tactile sensibility. As necessary, you may retest the patient, using another test form, to obtain a better index of sensibility (average the two scores, unless you suspect that the patient had misunderstood the original instructions).
Four random testing orders (forms) are encoded on one test sheet, please contact us to request the forms.
Testing with the ten-gram monofilament: "The two-out-of-three rule"
Patients with LOPS develop a foot ulcer much more frequently than those without LOPS.(1) Further, recent research demonstrates that older patients, especially women, with LOPS suffer falls more frequently.(2, 3) Nevertheless, diabetic patients are the usual target for LOPS testing. What is LOPS? An acronym for loss of protective sensation, LOPS occurs when patients fail to report the application of a ten-gram testing monofilament to their foot.
LOPS may have a spotty distribution across the foot that confounds reliable detection. Recent research has addressed alternative testing strategies for the detection of LOPS. For example, instead of using one application of a ten-gram monofilament, some researchers have investigated the use of several applications of the monofilament to increase the reliability and validity of the test for LOPS.
Altering the instrument or the procedure can increase sensitivity and specificity. Considering the instrument, you should only employ testing monofilaments that are factory calibrated for applied force. Connecticut Bioinstruments calibrates each monofilament by controlling the force that it applies. Additionally the use of a patented Softip™ monofilament reduces the variability of the perceived intensity, an important aspect of reliability. Considering the procedure, nonmedical research has uncovered a superior testing paradigm.(4) I call this procedure the two-out-of-three rule. The resulting testing paradigm both increases detection and specificity. Specificity increases because of the decrease in the false-positive rate. Define ten-gram sensation employing the criterion of at least two detections out of three monofilament applications. LOPS, then, is defined as not ten-gram sensation. Alternatively said, when testing one specific site, two or three failures to detect from three monofilament applications indicates LOPS. If the detection rate were to be 75%, you can achieve 84%. If the false-positive rate were to be 10%, you can achieve 3%. Other procedural changes can also improve reliability, e.g., by indicating the interval of potential stimulation.
Post script. The reported values are mathematically derived. As prerequisite for the testing paradigm, the patient must evaluate each application of the monofilament independently. Further, the criteria are consistent with each other, and each criterion weights the detection of LOPS to the same degree as the false-positive indication of LOPS. By consistent, I mean whatever result you would get on the average for a population of same patients using one stimulation of the monofilament, you will get the same result (i.e., detect or not) on the average (but with less variability on a patient by patient basis) using the rule two out of three.
1. McNeely, M.J., Boyko, E.J., Ahroni, J.H., Stensel, V.L., Reiber, G.E., Smith, D.G., & Pecoraro, R.F. (1995) The independent contributions of diabetic neuropathy and vasculopathy in foot ulceration. How great are the risks. Diabetes Care, (Feb.) 18(2), 216-219
1. Lord SR; Lloyd DG; Li SK Sensori-motor function, gait patterns and falls in community-dwelling women. Age Ageing 1996 Jul;25(4):292-9
2. Plummer ES; Albert SG, Focused assessment of foot care in older adults. J Am Geriatr Soc 1996 Mar;44(3):310-3
4. Weinstein, C., Drozdenko, R., and Weinstein, S. (November 13-15, 1991) The challenge of biodetection for screening persons carrying explosives. Presented at the First International Symposium on Explosive Detection Technology. FAA, New Jersey.