Dermatophyte Test Medium Culture for Evaluating Toenail Infections in Patients With Diabetes

Abstract

OBJECTIVE -To evaluate the performance of the in-office dermatophyte test medium (DTM) culture when used to confirm the diagnosis of onychomycosis in diabetic patients.RESEARCH DESIGN AND METHODS -Nail samples from 184 diabetic patients who exhibited symptoms consistent with toenail onychomycosis were screened for dermatophyte fungal infection using DTM, potassium hydroxide evaluation, and central mycology laboratory culture tests. The diabetic patient group investigated in this study is a subset of a heterogeneous set of patients who participated in a nationwide survey designed to investigate the use of fungal culture tests by dermatologists, podiatrists, and primary care physicians described in detail elsewhere. The overall sensitivity of the DTM and central laboratory culture methods was estimated and compared. Sensitivity differences between DTM and central laboratory culture methods were tested for statistical significance using the McNemar statistic.RESULTS -DTM culture was positive in 102 of 184 patients (55%), while the central laboratory culture test detected the existence of fungal infection in 78 of 184 (42%). The two tests were in agreement (both positive or both negative) in 114 of 184 patients (62%). Central laboratory culture identified dermatophytes as the pathogen in 91% of positive cases.CONCLUSIONS -DTM is a convenient and inexpensive culture test that can be used to confirm dermatophyte infections in diabetic patients with presumed onychomycosis. We found this test to be well suited for use in the primary care setting. Because oral antifungal agents are effective against dermatophyte species, which cause the vast majority of nail infections, diagnosis of onychomycosis requires confirmation of dermatophyte infection only, not identification of genus and species. DTM fulfills this requirement and has a diagnostic yield comparable to central laboratory culture.

Cost-effectiveness of diagnostic tests for toenail onychomycosis: A repeated-measure, single-blinded, cross-sectional evaluation of 7 diagnostic tests

“…Most studies report positivity rates without reference to a ''gold standard''; some of these studies are summarized in Table I. [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] The sensitivities of these tests are affected by practitioner experience, specimen collection methodology, and clinical onychomycosis pattern. [22][23][24] The purpose of this study was to estimate and compare the cost-effectiveness (utilizing sensitivity as the unit of effectiveness) of the most commonly used diagnostic tests: potassium hydroxide (KOH) alone (interpreted by a laboratory technician [KOH-LAB] and by a dermatologist [KOH-CLINIC]), KOH with dimethyl sulfoxide (KOH-DMSO) or chlorazol black E (KOH-CBE), culture with dermatophyte test medium (DTM), 25 culture with Mycobiotic and Inhibitory Mold Agar (Cx), and histopathologic analysis using periodic acideSchiff staining (PAS).…”

Onychomycosis: Sampling, diagnosing as efficiant part of hospital pharmacology

“…DTM is a medium that is used for isolation of dermatophytes. Th eir growth becomes visible when the yellow color of the medium changes to red, due to the presence of alkaline metabolites as a result of dermatophyte growth [25].Th is study showed that dermatophyte isolates have the biggest sensitivity to the DTM (33.4%). In most studies the common cause of onychomycosis is T. rubrum.…”

Unequivocal morphological diagnosis of fungi in morphologically abnormal nails

“…In climates where walking on bare feet is uncommon, fungal nail infections are often diagnosed; closed shoes tend to be worn all day in the Netherlands, for example, creating a favourable climate for fungal growth. Closed shoes are mainly and open sandals seldom worn by men 11–13 …”