A Retrospective Review of Diagnostic Testing for Onychomycosis of the Foot

Poor Antifungal Coverage for Onychomycosis in a Cross-Sectional Analysis of Medicaid Formularies

BACKGROUND

Onychomycosis is the most common nail disease seen in clinical practice. Medication safety, severity of disease, comorbidities, concomitant medications, patient age, and cost are all important considerations when treating onychomycosis. Because cost may affect treatment decisions, we sought to analyze Medicaid formulary coverage of onychomycosis antifungals.

METHODS

Public state Medicaid formularies were searched for coverage of US Food and Drug Administration-approved onychomycosis medications and off-label oral fluconazole. Total drug cost for a single great toenail was calculated using the National Average Drug Acquisition Cost. Pearson correlation coefficients were calculated to compare coverage and cost, mycologic cure rate, and complete cure rate.

RESULTS

Oral terbinafine and off-label fluconazole were widely covered for onychomycosis treatment. There was poor coverage of oral itraconazole and topical ciclopirox, and there was no coverage of topical efinaconazole and tavaborole without step-edits or prior authorization. There was a significant negative correlation between medication coverage and cost (r = -0.758; P = .040). There was no correlation between medication coverage and mycologic (r = 0.548; P = .339) and complete (r = 0.768; P = .130) cure rates.

CONCLUSIONS

There is poor Medicaid coverage of antifungals for the treatment of onychomycosis, with step-edits and prior authorization based on cost rather than treatment safety and efficacy. We recommend involving podiatrists and dermatologists in developing criteria for insurance approval of onychomycosis treatments.

Comparison of Fungal Fluorescent Staining and ITS rDNA PCR-based Sequencing with Conventional Methods for Diagnosis of Onychomycosis

Accurate identification of fungal causes for onychomycosis is essential for proper treatment. Presently available laboratory methods show unreliable sensitivity; so there is a requirement for innovative detection techniques. The aim for this work was to assess the efficiencies of fluorescent staining and internal transcribed spacer (ITS) ribosomal DNA (rDNA) polymerase chain reaction (PCR)-based sequencing in comparison to conventional techniques for diagnosis of onychomycosis. Nail specimens obtained from 100 patients with clinically- diagnosed onychomycosis were analyzed. Nail scrapings or clippings were subjected to direct microscopic examination by KOH mount, culture by using Sabouraud’s dextrose agar and histopathological examination with periodic-acid Schiff (PAS). Collected specimens were subsequently examined by fluorescent staining and PCR-based sequencing (30 specimens only) to compare the feasibility, sensitivity and diagnostic accuracy for these two methods. The most frequently isolated fungi were yeasts (39/76: 51.3%), dermatophytes (24/76; 31.6%) and non-dermatophyte molds (NDMs) (13/76; 17.1%). Mixed mycotic infections were recovered from 6% of the collected nail specimens. The positive detection rates were significantly different between KOH examinations (52%), nail plate histology (55%), fungal culture (70%) and fluorescent staining (80%). Considering fungal culture as the gold standard, the most sensitive technique was PCR (100%) followed by fluorescent staining (89%), PAS staining (69%) while the least sensitive technique was KOH mount (53%). Fluorescence staining can be used as a rapid and high-yield technique for identification of fungi in the specimens. PCR-based sequencing was highly sensitive and faster compared to culture. Whenever possible, it enables species identification with higher adequacy.

Onychomycosis and Tinea Pedis in the Feet of Patients With Diabetes

This study aimed to determine the prevalence of onychomycosis and interdigital tinea pedis in a cohort of Spanish patients with diabetes in whom onychomycosis was clinically suspected (n = 101). Samples from a first toenail scraping and the fourth toe clefts were subjected to potassium hydroxide direct vision and incubated in Sabouraud and dermatophyte test medium. Fifty-eight samples were also analyzed by a pathologist using periodic acid-Schiff staining and Calcofluor white direct fluorescence microscopy. Onychomycosis was only confirmed in 41 patients (40.6%). The most frequent aetiological agent was Trichophyton rubrum, isolated in 10 patients (36%), followed by Candida parapsilosis in 7 patients (25%). Tests on the fourth toe cleft samples were only positive in 11 patients (10.9%), and in all cases, onychomycosis was also diagnosed. Neuroischemic foot was the only significant variable associated with onychomycosis in the univariate analysis (P < .01). A positive result for mycosis in the fourth toe cleft was found in 11 cases (10.9%) and was associated with a history of myocardial infarction (P< .01; odds ratio [OR]: 84.2, confidence interval [CI]: 6.8-1036.4) and neuroischemic foot (P< .01; OR: 13.7, CI: 12.6-71.6) in the multivariate model. In conclusion, the prevalence of onychomycosis and tinea pedis in patients with diabetes in whom onychomycosis was clinically suspected was 40.6% and 10.9%, respectively. In addition, onychomycosis was not always associated with tinea pedis. These results show that clinical diagnosis has low accuracy in people with diabetes mellitus, and that diagnosis should not be based on clinical toenail characteristics alone.

PAS and GMS utility in dermatopathology: Review of the current medical literature

The American Society of Dermatopathology has established an Appropriate Use Criteria (AUC) Committee with the intention of establishing evidence-based recommendations regarding the appropriateness of various ancillary tests commonly utilized by dermatopathologists. Periodic acid Schiff (PAS) and Grocott (or Gomori) methenamine silver (GMS) stains represent some of the most commonly employed ancillary tests in dermatopathology. The utility of these tests was targeted for evaluation by the AUC. This literature review represents a comprehensive evaluation of available evidence for the utility of PAS and/or GMS staining of skin and nail biopsies. In concert with expert opinion, these data will be incorporated into future recommendations by the AUC for PAS and GMS staining in routine dermatopathology practice.

Liquid chromatography-tandem mass spectrometry is effective for analysis of ergosterol in fungal-infected nails

BACKGROUND

Identification of onychomycosis is mainly based on clinical diagnosis with auxiliary diagnostic methods such as potassium hydroxide (KOH) microscopy, periodic acid-Schiff staining or fungal culture. However, each method is limited by its sensitivity and specificity.

AIM

To develop a new test method using the common fungal end product, ergosterol, and investigate if it can be used as a new diagnostic tool.

METHODS

We collected consecutive data from 20 participants with nail problems. Following clinical diagnosis, samples were taken for KOH microscopy and for mass spectrometry (MS) to check for the presence of ergosterol.

RESULTS

Of the 20 cases collected, 7 were positive for fungal infection by MS. Four of these were already suspected to have onychomycosis, whereas one of the remaining three subjects was presumed to have dry nail and the other two to have onycholysis. The MS test seemed to be better at detecting combinations of nail conditions. Conversely, of the five patients clinically diagnosed as having onychomycosis, four had a positive MS result, whereas the fifth had negative results on both KOH and MS. Two other participants had a positive KOH test and were also found to have positive MS results.

CONCLUSION

Detection of the presence of ergosterol by MS seems to be a useful tool for confirming onychomycosis. However, further studies are needed to verify the sensitivity and specificity of this MS method.

Etiology of Onychomycosis in Patients in Turkey

BACKGROUND

Onychomycosis is a chronic nail infection caused by dermatophytes, Candida, nondermatophyte molds, and Trichosporon. The purpose of this study was to identify the underlying pathogen in patients with onychomycosis in our region.

METHODS

A retrospective analysis of 225 cases with onychomycosis, diagnosed over a 27-month period at the Department of Dermatoveneorology, Bezmialem Vakif University, Istanbul, Turkey, and confirmed with culture, was performed.

RESULTS

Patient age ranged from 2 to 87 years (mean ± SD, 41.59 ± 17.61), and female patients were more commonly affected (120 cases, 53.3%) than male patients. Lateral and distal subungual onychomycosis was detected in 180 cases (80%). Etiologic agents were as follows: Trichophyton rubrum, 77 cases (34.2%); Trichophyton mentagrophytes, 30 cases (13.3%), Candida albicans, 28 cases (12.4%); Candida parapsilosis, 25 cases (11.1%); Acremonium species, one case (0.4%); Aspergillus species, two cases (0.9%); Fusarium species, four cases (1.3%); and Trichosporon species, three cases (1.3%).

CONCLUSIONS

The most frequent isolated etiologic agents were T rubrum for toenails and C albicans for fingernails.

Evaluation of a new fluorescent reagent, fluorescent brightener 85, for the diagnosis of suspected onychomycosis compared with potassium hydroxide

Onychomycosis is a common fungal infection in dermatology clinics. The commonly used diagnostic method, potassium hydroxide (KOH) direct microscopy, does not have a high-positive detection rate. Therefore, a new diagnostic method is needed to confirm onychomycosis. The objective of this research was to use fluorescent brightener 85 (FB 85), a new fluorescent reagent for fungi detection, and to evaluate this new method based on the diagnostic positive rate, accuracy and efficiency in suspected onychomycosis compared with the KOH method. Subungual debris was collected from clinically suspected onychomycosis cases and divided into two parts. The parts were examined by FB 85 and 10% KOH solution, respectively. In total, 108 patients with suspected onychomycosis were recruited. The positive rates of FB 85 and KOH were 88.9% and 55.6%, respectively. The patients showed significant statistical differences (P < .001). Compared with the KOH method, the FB 85 fluorescent method was an accurate and efficient method with a higher positive rate. This method could increase the diagnostic accuracy and efficiency of onychomycosis detection.

Point-of-Care Diagnosis of Onychomycosis by Dermoscopy

BACKGROUND

Onychomycosis is one of the most common diseases of the toenails. The costs of diagnosis and treatment are substantial, and as the population ages, the overall cost burden will continue to escalate. The purpose of this study was to correlate dermoscopic features with pathologic diagnosis to support the accuracy of point-of-care diagnosis by dermoscopic examination.

METHODS

Nail unit pathology reports of 52 patients with abnormal great toenails were compared with the dermoscopic features detected by nail unit dermoscopy.

RESULTS

The dermoscopic analysis predicted the laboratory diagnosis in 90.4% of the study patients. The specific dermoscopic findings of short spikes (P < .001), long striae (P < .001), aurora borealis (P < .001), irregular termination (P = .003), dermatophytoma (P = .011), transverse onycholysis (P = .018), and dry scale (P = .04) patterns were all significantly associated with pathology test results consistent with oncyhomycosis. Transverse onycholysis (P = .018) was significantly associated with negative pathology results consistent with the diagnosis of nail dystrophy.

CONCLUSIONS

Point-of-care examination by dermoscopy positively correlates with histopathologic tests and could be used to diagnose onychomycosis while reducing diagnostic costs.

Reappraisal of Conventional Diagnosis for Dermatophytes

Dermatophytoses include a wide variety of diseases involving glabrous skin, nails and hair. These superficial infections are a common cause of consultation in dermatology. In many cases, their diagnosis is not clinically obvious, and mycological analysis therefore is required. Direct microscopic examination of the samples using clearing agents provides a quick response to the clinician and is usually combined with cultures on specific media, which must be used to overcome the growth of contaminating moulds that may hamper the recovery of dermatophytes. Accurate identification of the causative agent (i.e. at the species level), currently based on morphological criteria, is necessary not only to initiate an appropriate treatment but also for setting prophylactic measures. However, conventional methods often lack sensitivity and species identification may require up to 4 weeks if subcultures are needed. Histological analysis, which is considered the "gold standard" for the diagnosis of onychomycoses, is seldom performed, and as direct examination, it does not allow precise identification of the pathogen. Nevertheless, a particular attention to the quality of clinical specimens is warranted. Moreover, the sensitivity of direct examination may be greatly enhanced by the use of fluorochromes such as calcofluor white. Likewise, sensitivity of the cultures could be enhanced by the use of culture media containing antifungal deactivators. With the generalization of molecular identification by gene sequencing or MALDI-TOF mass spectrometry, the contribution of historical biochemical or physiological tests to species identification of atypical isolates is now limited. Nevertheless, despite the recent availability of several PCR-based kits and an extensive literature on molecular methods allowing the detection of fungal DNA or both detection and direct identification of the main dermatophyte species, the biological diagnosis of dermatophytosis in 2016 still relies on both direct examination and cultures of appropriate clinical specimens.