I read with interest the "Vignette," "Sensitivity and Specificity of Potassium Hydroxide Smears of Skin Scrapings for the Diagnosis of Tinea Pedis," by Miller and Hodgson,1 which appeared in the April 1993 issue of the Archives. The conclusion of their article was that "our findings support the use of cultures as a confirmation of the findings seen on the potassium hydroxide smear." The authors came to this conclusion because 41% of potassium hydroxide—positive specimens did not show fungal growth in culture. Furthermore, they found that only 77% of culture-positive specimens were read as potassium hydroxide positive.
I think their findings and conclusions should be interpreted with caution. These results might suggest that even the potassium hydroxide smear, one of the few "waived" tests in CLIA (Clinical Laboratory Improvement Amendments of 1988) should come under more scrutiny and regulation. I think it is noteworthy that the slides were read by
Salomon RJ. The Sensitivity and Specificity of the Potassium Hydroxide Smear. Arch Dermatol. 1993;129(10):1342. doi:10.1001/archderm.1993.01680310114024