Diagnostic values of KOH examination, histological examination, and culture for onychomycosis: a latent class analysis.

BACKGROUND: In the absence of a real gold standard, comparative studies are still done on diagnostic methods for onychomycosis. There are only a few attempts using latent class analysis to determine the value of polymerase chain reaction in comparison to conventional methods. We aimed to determine the value of histological examination in such a way for the diagnosis of onychomycosis. METHODS: Potassium hydroxide mount (KOH), culture and histological examination with periodic acid-Schiff (PAS), and Gomori's methenamine silver (GMS) stains were done in 106 patients having clinically suspected toenail onychomycosis. RESULTS: KOH was positive in 74% of the patients; culture in 14%; PAS in 30%; and GMS in 66%. According to the results of the latent class analysis, culture and PAS were highly specific but poorly sensitive; KOH, highly sensitive but poorly specific; and GMS, both highly sensitive and specific. CONCLUSIONS: Based on these results, we have proposed KOH as a screening test and GMS as a confirmatory test for the diagnosis of onychomycosis in our own practice. However, since positivity rates of different diagnostic methods vary widely in different centers, it is more suitable that every center should determine their own diagnostic strategy by evaluating their own results with latent class analysis.

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.

Variables affecting interpretation of skin prick test results.

BACKGROUND: Both performer- and device-dependent variabilities have been reported in sizes of wheal responses to skin prick tests. OBJECTIVE: We aimed to evaluate whether or not variabilities in sizes of wheal responses influence the final interpretation of skin prick tests; in other words, the decision on whether or not there is an allergy to a given antigen. METHODS: Skin prick tests with positive and negative controls and extracts of Dermatophagoides farinae and Dermatophagoides pteronyssinus were done for 69 patients by two different persons, using two different puncturing devices- disposable 22-gauge hypodermic needles and metal lancets. RESULTS: Among four different skin prick tests, the average coefficients of variation in sizes of wheal responses were near to or higher than 20% for all of them. On the other hand, in the final interpretation of results, kappa values indicated substantial or almost perfect agreements between these tests. However, the frequency of establishing allergy to the house dust mites widely ranged in these tests (20.8-35.8% for D. farinae and 20.8-28.3% for D. pteronyssinus). LIMITATIONS: The conduction of the study in a single center and the comparisons of results of only two performers. CONCLUSION: We feel that variabilities in sizes of wheal responses of skin prick test can influence its categorical results.

Granulomatous disorders.

Almost all granulomatous skin disorders can cause red lesions on the face. Such disorders may include many bacterial, fungal, or parasitic infections, noninfectious inflammatory disorders, foreign body reactions, and even neoplasms. Clinically, they usually present with papules, plaques, nodules, and/or abscesses, which may ulcerate. It may be helpful in their differential diagnosis to define certain clinical patterns, such as multiple and discrete papules, necrotic or umbilicated papules or nodules, annular plaques, vegetative plaques or tumors, verrucous plaques or tumors, abscesses and/or sinuses, and lymphocutaneous pattern. Some disorders, such as sarcoidosis, can cause a wide variety of lesions. We accept that cutaneous leishmaniasis is also among such great imitators.