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Electronic letters published:
![[Read Comment]](/icons/misc/sectionDOWN.gif){kind=icon}
Do not reject the good with the bad.
Response to Dr Oyer
Accuracy of Monofilament Testing to Diagnose Peripheral Neuropathy
The Clanging Tuning Fork Test for Diabetic Neuropathy
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Kees J Gorter, Utrecht, The Netherlands GP PhD, Julius Center for Health Sciences and Primary Care; Dpt of General Practice Univ Utrecht
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The meta-analysis of Dros et al. is a robust piece of work, but the introduction of their article may give rise to a discussion about the value of the Semmes Weinstein monofilament. However, the use of a monofilament in screening and follow-up of patients at risk for a foot ulcer is not an outcome of their study. Indeed, in the introduction they state that timely identification of loss of protective sensation (LPS) may allow preventive interventions to reduce the risk of (diabetic) foot ulcers. But in the conclusion they state that the sole use of monofilament test to diagnose peripheral neuropathy is not recommended. Several guidelines recommend the use of monofilament test to screen for LPS. But based on the study of Dros et al. some might conclude that monofilaments should not be used as a single test to detect LPS. This of course would reject the good with the bad. In the pathofysiology of diabetic foot ulcers both LPS, peripheral arteriosclerotic vessel disease, limited joint mobility and level of glycaemic control play an important role. Due to loss of protective sensation, increased pressure, caused by change in position of the feet and in gait by diabetic neuropathy, may damage subcutaneous tissue without alarming the patient [1]. The International Diabetes Federation recommends an annual foot exam for every patient with T2DM to prevent foot ulcers. It is expected that in 2010 there will be 211 million people with Type 2 Diabetes Mellitus (T2DM). Since most of these are treated in primary care, a simple but effective screening tool as Semmes Weinstein monofilament should be used to detect LPS, since this is a good predictor of foot ulcers [2]. During the annual foot exam, individual risk will be stratified to determine the frequency of follow-up exams [3]. This follow- up of LPS will also be carried out by 10 grams monofilament. Therefore monofilaments play an important role in screening and follow up of LPS but are not recommended as a single instrument to diagnose peripheral neuropathy. [1] Bolton AJ. The diabetic foot from art to science. Diabetologia
2004; 47:1343-53.
Competing interests: None declared |
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Jacquelien Dros, Amsterdam, the Netherlands GP-researcher, Department of Family Medicine, Academic Medical Center, University of Amsterdam
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The Accuracy of Monofilament Testing to Diagnose Peripheral Neuropathy: a Systematic Review. In our conclusion on monofilament testing we state that little can be said about the test accuracy for detecting neuropathy in feet. No more, no less. Despite the frequent use of the monofilament test, especially in patients with diabetes, its value has not been empirically proven. But what has not been proven is not necessarily not worthwhile or not true. There has to be done more diagnostic research on monofilament testing according to STARD-criteria: complete and informative reporting of results from monofilament testing compared with the reference standard (until now nerve conduction studies). In this future research there should be eye for optimal test application (one toe or more sites? and which sites?) and defining thresholds (which and how many sites have to be abnormal to call a monofilament test positive?). Oyer is describing interesting outcomes of his studies with the tuning fork test. However, a major flaw in his diagnostic study is the lack of a reference standard. If we really want to know the diagnostic accuracy of the tuning fork test we should conduct a systematic review of primary studies on tuning fork tests with meta-analysis. That the tuning fork test should be the test for both neuropathy and increased risk of foot ulcers is too early to conclude. Meanwhile, the sole use of a monofilament test or tuning fork test to diagnose peripheral neuropathy is not recommended. The diagnosis of peripheral neuropathy can be made only after a careful clinical examination with more than 1 test, as recommended by the American Diabetes Association. Tests for this clinical examination are vibration perception (using a 128-Hz tuning fork), pressure sensation (using a 10-g monofilament at least at the distal halluces), ankle reflexes, and pinprick. When in doubt, a nerve conduction test might be necessary to establish a firm diagnosis. Jacquelien Dros, MD Competing interests: None declared |
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Bernhard Schaller, Romania Univrersity of Oradea, Nora-Mihaela Sandu
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The diagnosis and treatment of peripheral neuropathy has gained increased interest during the last years (1); not at least as it is the most common neurologic complication of HIV infection and a major cause of morbidity in HIV-infected patients (2). Peripheral neuropathy is increasing to occur secondary to HIV or be due to antiretroviral drug toxicity (2). Timely detection of the symptoms and signs of peripheral neuropathy in patients who have HIV may allow for the reversal of the toxic effects of antiretrovirals and for the initiation of symptomatic treatment. However, as around 50% of peripheral neuropathy are symptomless, there is a need of an inexpensive painless, easy to administer and acceptable to patients bedside diagnostic test. The (Semmes- Weinstein) monofilament test is such a test that is often mentioned in international guidelines. For these reasons, the work of Dros et al. (3) sheds an important light on the fact that diagnostic studies with adequate methodology are lacking for this test. Even so, the study of Dros et al. (3) has defined clear and well-acceptable inclusion criteria, the questions raises whether the predictive value of this test is really so bad as the authors conclude. Of course, a standardization of the test is desirable, but from the practical point of view, it is sufficient to standardize it locally. We think therefore that this conclusion is not correct, as it is difficult to define a gold-standard. From point of view of the predictive value, the gold standard must be the biopsy, from the clinical pathway it is more the electrophysiological examination. We have to accept that we are on times with an enormous economic burden on the health care system. From this context, the cost-effectiveness of screening test - like the (Semmes-Weinstein) monofilament test is - is as important as the predictive value. To our opinion, further studies should also focus on that. The (Semmes-Weinstein) monofilament test is therefore a valuable and most-probably cost-effective screening test; no more, but also no less! References:
Competing interests: None declared |
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David S. Oyer, Chicago, USA Endocrinologist, Assistant Professor of Clinical Medicine, Northwestern Feinberg School of Medicine
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The meta-analysis by Dros et al confirms what is clinically obvious. The ability of a patient to accurately detect the 10-gm monofilament is not a good test for diabetic neuropathy. The 10 gm monofilament test becomes abnormal late in the course of diabetic neuropathy. Vibration testing can demonstrate severe neuropathy years earlier than the 10-gm monofilament. David Saxon, Ajul Shah and I described a simple, accurate and reproducible procedure using the tuning fork in an article entitled “Quantitative Assessment of Diabetic Peripheral Neuropathy with use of the Clanging Tuning Fork Test” in Endocrine Practice 2007;13(1):5-10. In a follow-up study published in Diabetes 2008; 57(S1)A2340 PO, Dr. Hai, Susan Bettenhausen and I showed that the CTF is more sensitive for detecting neuropathy than the 10-gm monofilament and is also more sensitive for detecting increased ulcer risk. When severe neuropathy was present by the CTF test (4 seconds or less) the 10-gm monofilament was still normal in 68% of patients. When the CTF score was 0 seconds, 33 % still had normal 10-gm monofilament tests. So the 10-gm monofilament is both insensitive and inaccurate in diagnosing diabetic neuropathy. Monofilament testing becomes abnormal about 2-3 years after vibration sense is lost completely by the CTF technique. The monofilament is thought to have value as a predictor of increased risk of foot ulcer. It is true that an abnormal 10-gm monofilament test indicates an increased risk of ulcer, but the foot has already been at increased risk for years! In our study, 5 of 21 ulcers occurred in patients with normal 10-gm monofilament tests but CTF scores of 4 seconds or less. All of the ulcer patients had CTF scores of 4 seconds or less. There is no value in 10-gm monofilament testing if the CTF score is 5 seconds or more because it is normal 100 % of the time. And with CTF scores of 4 seconds or less, severe neuropathy and increased ulcer risk are demonstrated. So I see no value in doing monofilament testing. Of course, when a patient has an ulcer, you can dispense with any testing, because the patient has already demonstrated neuropathy and an increased ulcer risk. The CTF test should be the test for both neuropathy and increased risk of foot ulcers. As we call it, the CTF test is “the A1C of the foot”. David S. Oyer, MD, FACE Competing interests: None declared |
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