Successive Potassium Hydroxide Testing for Improved Diagnosis of Tinea Pedis
In this study, we investigated the role of successive potassium hydroxide (KOH) tests for the diagnosis of tinea pedis with different clinical presentations. The study included 135 patients with 200 lesions that were clinically suspicious for tinea pedis. Three samples of skin scrapings were taken from each lesion in the same session and were examined using a KOH test. This study offers an inexpensive, rapid, and useful technique for the daily practice of clinicians and mycologists managing patients with clinically suspected tinea pedis.
Practice Points
- At least 2 samples should be taken for potassium hydroxide examination when tinea pedis is sus-pected clinically.
- The number of samples should be at least 3 if keratotic lesions are present.
Conclusion
In this study, we investigated the benefit of successive KOH testing in the laboratory diagnosis of tinea pedis and found that the use of second samples in particular provided a substantial increase in diagnostic yield. In other words, the utilization of successive KOH testing remarkably improved the diagnosis of tinea pedis. Therefore, we suggest that at least 2 samples of skin scrapings should be taken for the diagnosis of tinea pedis and that the number of samples should be at least 3 for keratotic lesions. However, further study by using a gold-standard method such as a molecular-based assay as well as taking the samples in daily or weekly intervals is recommended to achieve a more reliable result.
Acknowledgment
The authors would like to thank Gökçen Şahin (Adana, Turkey) for providing technical support in direct microscopic examination.
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