- Ivan Bristow
How easy is it to diagnose tinea?
Dermatophyte skin infection affects around 25% of the global population (1) making it one to the world’s leading diseases. Being such a common problem, one would hope that the condition would be easily recognised by health care professionals and patients alike, but that isn’t always the case.
From a patients perspective, recognising a fungal foot infection can be problematic. As we know as clinicians on a daily basis patients present with fungal foot infection that they are totally unaware of. A study at a diabetes conference for patients demonstrated in a sample of 95 delegates, a high prevalence of fungal foot disease (skin and nail infection) with a low recognition rate by the sufferer (2). But why is that? If the condition doesn’t bother you then it’s not likely to be recognised?
One piece of research demonstrated that self-recognition maybe related to the symptoms. In a survey of 377 factory workers (3), there were 41 cases of undiagnosed (“occult”) fungal foot infection. When researchers analysed the undiagnosed cases along with self-diagnosed cases they discovered that itching and redness were more common in the self-diagnosed group suggesting that a patient diagnosis is only made by the sufferer when the symptoms are distracting or unsightly. This would fit the theory - as we know, the most common infection T rubrum is often asymptomatic and invisible for many being present on the (rarely inspected) plantar surface, mimicking dry skin (4).
So, can health care professional do any better in recognising it? In a paper published in the Journal of the American Academy of Dermatology (5), a researcher asked an audience of dermatologists to diagnose superficial skin infections from 13 slides which were presented at a infection-themed meeting. They were simply asked if it was a fungal infection or not. Amongst the group although they were around 75% accurate in their responses, but for only 1 case out of the 13 did more than 90% of the audience agree.
Moving closer to fungal nails, a Japanese study (6) collected and analysed nail samples from 113 nails, which were subsequently photographed and categorised as being mycotic or not. Thirty-one dermatologists then were asked to make a visual diagnosis of “fungal or not”. In consequence, they were shown to have an accuracy of 67% - roughly two-thirds. This concurs with earlier studies of visual diagnosis (7). Analysis of the data showed that those with less than a year’s dermatological experience we less likely to achieve the correct diagnosis but more interestingly, having increasing years’ experience as a dermatologist did not improve diagnostic accuracy either.
Lack of recognition and mis-diagnosis is a common theme in tinea and as one paper suggested - it is all too easy to make a diagnosis on visual inspection alone and then only consider appropriate testing when the prescribed treatment fails (8). Consequently, it always advised best practice to consider testing before commencing treatment (9-12) to avoid inappropriate care.
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2. Mayser P, Hensel J, Thoma W, Podobinska M, Geiger M, Ulbricht H, et al. Prevalence of fungal foot infections in patients with diabetes mellitus type 1 - underestimation of moccasin-type tinea. Exp Clin Endocrinol Diabetes. 2004;112(5):264-8.
3. Maruyama R, Hiruma M, Yamauchi K, Teraguchi S, Yamaguchi H. An epidemiological and clinical study of untreated patients with tinea pedis within a company in Japan. Mycoses. 2003;46:208-12.
4. Bristow IR. Fungus the forgotten Infection In: Cherry GW, Hughes M, editors. The Second European Wound Healing Course Handbook. Oxford: Positif Press; 2010.
5. Yadgar RJ, Bhatia N, Friedman A. Cutaneous fungal infections are commonly misdiagnosed: A survey-based study. J Am Acad Dermatol. 2017;76(3):562-3.
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9. Eisman S, Sinclair R. Fungal nail infection: diagnosis and management. BMJ. 2014;348.
10. Ameen M, Lear JT, Madan V, Mohd Mustapa MF, Richardson M. British Association of Dermatologists' guidelines for the management of onychomycosis 2014. Br J Dermatol. 2014;171(5):937-58.
11. Bristow IR. Be sure of the cure when treating onychomycosis. Podiatry Now. 2017;20(1):14-6.
12. de Berker D. Clinical practice. Fungal nail disease. N Engl J Med. 2009;360(20):2108-16.