An alternative to a 10-g monofilament or tuning fork? Two new, simple, easy-to-use screening tests for determining foot ulcer risk in people with diabetes

Authors


Diabet. Med. 29, 1–2 (2012)

‘Coming events cast their shadow before them’. This quote from could not be more appropriate when screening and risk stratifying those people with diabetes who are at greatest risk of foot ulceration and potential lower extremity amputations. It is well known that these advanced and complex diabetes complications place a huge burden upon healthcare resources [1]. A recent publication estimated that, for every £150 spent on health, £1 is spent directly on diabetic foot disease management [2]. Current National Institute of Health and Clinical Excellence guidelines recommend that people with diabetes should have annual foot examinations to identify, stratify and implement care where required [3,4]. These recommendations have been fairly well adopted within most primary care settings, with the Quality and Outcome Framework driving diabetes consultations including foot screening for sensory loss using either a 10-g monofilament and/or a 128-Hz tuning fork and lower limb peripheral obstructive arterial disease by pedal pulse palpation [4–7]. More recently, the Quality and Outcome Framework targets have been introduced aimed at ulcer risk stratification; sadly, implementation of prevention programmes was not included in this.

Perhaps one primary care area where sensory testing to identify ulcer risk is suboptimal is within nursing, residential and care homes. This is also true for patients admitted to hospital. In both of these environments, heel pressure sores are far too common because of immobility and unnoticed sensory loss. The presence of peripheral sensory neuropathy is undoubtedly the most important risk factor for foot ulceration and potential amputation. Thus, any simple, reliable, robust and easy-to-use tools that can be used to identify those at risk of ulceration attributable to sensory loss should be welcomed and adopted in all care settings. More importantly, a tool that could be used reliably by all healthcare professionals or, indeed, patient carers with little training, would be groundbreaking.

Epidemiological data from a large European prospective study involving 16 countries showed a prevalence rate for sensory neuropathy of 28% [8], and several other population and clinic-based studies have shown rates between 30 and 50% [9–11]. These data are now outdated, with no current robust studies to give us a clear picture of neuropathy prevalence today; however, it is clear that, with increasing diabetes prevalence, especially Type 2 diabetes, peripheral sensory neuropathy and foot ulceration risk is likely to increase significantly. A recent publication, which reported the introduction of a standardized screening and risk stratification programme across the whole of Scotland, showed that ulcers were 83 and 6 times more common in the high- and moderate-risk stratified groups [12]. Thus, screening and risk stratification with validated tools are prerequisites to reducing the burden of diabetic foot complications.

Two recent studies published in this issue of Diabetic Medicine examine new and potentially exciting tests of sensation. Both papers examine the same new test, whilst one paper also examines a second new test; in both papers the tests are compared with well-reported, reliable and accepted ‘gold standard’ sensory screening tests. The gold standard methods are vibration perception thresholds (VPT), and the Neuropathy Disability Score, which is a combination of 10-g monofilament, ankle reflex and vibration with a tuning fork, Neurotip™ and temperature sensation.

The new test that is common to both papers is a small pocket-sized battery-powered vibrating device that is disposable, the VibraTip™. This device is said to replicate a 128-Hz tuning fork and to be used similarly at the tip of the great toe.

The second test, reported in only one of the papers, needs no equipment at all, but relies on the testers’ sensitivity to light touch with their own finger—the Ipswich Touch Test. Both tests are simple and easy to use, with little training required. Their reliability has been tested in relatively small sample sets; Bracewell et al. [13] include 141 subjects, while Bowling et al. [14] studied 83 subjects. The study by Bracewell et al. examined the Vibratip in a secondary care outpatient setting. There is little information given regarding the characteristics or selection process of the subjects, except they had Type 1 or Type 2 diabetes, were matched for age and sex, and 11% had a history of foot ulceration. All tests were performed by one researcher only. The authors report a 41% prevalence of neuropathy using a neurothesiometer to obtain vibration perception thresholds for each subject. A previous study compared the VibraTip with both 10-g monofilament and 128-Hz tuning fork and found a good agreement [15]. Bracewell et al. also tested the Vibratip against these and, additionally, against the Neurotip. More importantly, all of these were compared with the gold standard of vibration perception thresholds obtained by neurothesiometry. Testing at five sites on each foot, they report almost identical performance characteristics with the new device and 10-g monofilament; additionally, the intra-rater reliability for VibraTip was good.

The study by Bowling et al. [14] was undertaken in community and hospital settings with data obtained by eight healthcare professionals. The sample group was small with 83 subjects in total, with similar limited demographic data presented, but also included diabetes duration and BMI. This study examined both the VibraTip and the Ipswich Touch Test and compared them to the well-validated Neuropathy Disability Score and vibration perception threshold measured by neurothesiometry. Unlike the study of Bracewell et al. [13], both the VibraTip and the Ipswich Touch Test were used at the recommended sites only and by eight independent operators. Similarly in this study, the performance characteristics of each of the new tests compared well with vibration perception threshold and Neuropathy Disability Score, having almost perfect agreement for all statistical parameters.

There is of course no perfect test that would meet all the requirements of busy clinical practice and clearly there are pitfalls and strengths with each of the screening devices and techniques. It is important not to lose sight of the rationale and expected outcomes of screening when deciding upon which screening tests should be adopted. Clearly, the Quality and Outcomes Framework requires a 10-g monofilament or 128-Hz tuning fork to be used and, thus, I feel these will continue to be the screening tools used for the time being.

So where do these new tools sit? Both are easy to use, one incurs cost and has a limited life of use, the other has no cost but has a potential larger margin of error because of the amount of applied digital pressure. However, both techniques could be reliably taught to any healthcare professional or carer, which would lend them to be used either for self-monitoring or in specific settings. Therefore, either of these tests could be effectively introduced to nursing, residential and care homes and all hospital wards to help identify those patients at greatest risk of heel sores. These lesions in the elderly are difficult to treat and have a high risk for amputation; thus, in these clinical settings, being able to identify and manage patients at high risk of pressure sore quickly and reliably would be immensely beneficial. Equally, training patients’ carers to screen for sensory loss with these tests regularly could have a significant impact on annual diabetes reviews and prevent devastating diabetic foot complications.

Competing interests

Nothing to declare.

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