Comparison between PAS and GMS stains for the diagnosis of onychomycosis

Background: Onychomycosis is the most common nail disease in adults. Periodic acid‐Schiff (PAS) stain has been considered the most sensitive method for diagnosis. By comparing originally stained PAS slides (i.e. without repeating PAS) with newly stained Grocott methenamine‐silver (GMS) slide, D’Hue et al. concluded that GMS is superior to PAS. We conducted a similar study with the addition of repeating PAS stain and compared the newly stained PAS and GMS slides in tandem. Methods: We performed both PAS and GMS stains on 30 clinically suspected onychomycosis cases. The presence or absence of fungal organisms was evaluated. The results were also compared with the original PAS stain. Results: Twenty‐two cases were positive with PAS, staining three cases more than GMS, which stained only 19 cases. The difference between the two stains is statistically insignificant. Repetition of GMS stain on these three cases (cutting in a deeper level in the paraffin block) resulted in positive results. Four out of 30 cases were negative with original PAS stain, but stained positive both with new PAS and GMS. Conclusions: PAS and GMS stains are quantitatively similar. Sensitivity of both methods can be increased by preparing two slides from different levels in the paraffin block. Reza Kermanshahi T, Rhatigan R. Comparison between PAS and GMS stains for the diagnosis of onychomycosis.     

PAS is optimal for diagnosing onychomycosis

Onychomycosis is a frequently treated fungal infection of the nail plate with morbidity in high‐risk populations. The diagnosis often relies on histopathologic analysis of nail plate specimens with the assistance of special stains. Pathologists utilize periodic acid schiff (PAS) and/or Gomori methenamine silver (GMS) stains to highlight fungi within the nail plate. In a recent study of 51 PAS‐negative nail cases, it was concluded that GMS is superior to PAS in the diagnosis of onychomycosis. We expand on this study by investigating a larger number of PAS‐negative nail clippings determining whether GMS or PAS is superior in highlighting fungi in additional sections. There was no difference in the sensitivity of PAS vs. GMS (4.2 vs. 4.3%, p = 0.57); however, PAS was found to be significantly less expensive by 2.6‐fold. Taken together, these data suggest that the PAS stain is the optimal method for diagnosing onychomycosis. Barak O, Asarch A, Horn T. PAS is optimal for diagnosing onychomycosis.     

The diagnosis of onychomycosis

The prevalence of onychomycosis is increasing and the primary pathogens may be dermatophytes, nondermatophyte molds, or Candida spp. It may not be satisfactory to treat onychomycosis on the basis of clinical diagnosis alone. Laboratory diagnosis is an important component of the proper management of this fungal infection. Laboratory diagnostic methods for detecting onychomycosis include light microscopy and culture, or histopathology. Management of onychomycosis includes palliation achieved through mechanical debridement of the nail and topical or oral antifungal therapy.     

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.     

甲真菌病的实验诊断研究

为寻找一种准确的甲真菌病的实验诊断方法,对５４例拟诊为甲真菌病的病甲分别采用直接镜检、真菌培养组织病理学方法进行对比研究,时取６例病甲进行扫描电镜观察。结果显示用３种方法检查甲真菌 阳性率分别为７２．７７％、７０．３７％、８７．０４％。     

Usefulness of histological examination for the diagnosis of onychomycosis.

BACKKGROUND: Direct microscopy and culture tests currently used in the diagnosis of nail mycosis can yield false-negative results, and confirmation of the pathogenic agent, especially in non-dermatophyte infections, is often a lengthy process. OBJECTIVE: The aim of this study was to investigate the usefulness of the histological examination of nail clipping samples in supplementing the standard microscopic and culture techniques for the diagnosis of onychomycosis. PATIENTS AND METHODS: One hundred and seventy-two subjects affected by nail alterations suggestive of onychomycosis were evaluated. Nail specimens were studied with 3 different techniques: direct microscopic examination of a 40% KOH clarified preparation, fungal culture and histological examination. Patients positive for fungal infection were re-evaluated with the same techniques after treatment with oral terbinafine, fluconazole or itraconazole and topical application of bifonazole or ciclopirox for 2 months. RESULTS: Direct microscopy was positive in 102 (59.3%) nail specimens. The culture test was positive in 90 cases (52.9%), showing a dermatophyte in 45, a yeast in 23 and a mould in 22 samples. The histological examination was positive in 94 (54.6%) samples. In 4 cases, it was the only investigation confirming the clinical diagnosis of nail mycosis. In most of the cases, the morphological aspect of the hyphae and/or spores suggested also to which group of pathogens (dermatophytes, yeasts or moulds) the mycetes observed in the histological sections could be ascribed. The concurrent presence of a dermatophyte and a mould was evidenced in a few specimens. The control histological examination at the end of the treatment showed negative results or residual non-vital hyphae and/or spores. CONCLUSIONS: Results of the present study indicate that the histological examination of nail clipping specimens is a relatively inexpensive, rapid and easily performed procedure. It is useful to confirm or refute the results of routine microscopy and culture tests. Moreover, nail histopathological observation may help in ascribing a pathogenic role of non-dermatophyte isolates and evaluating the effectiveness of antifungal treatment.     

A nail drilling method suitable for the diagnosis of onychomycosis

We describe a nail drilling method suitable for the diagnosis of onychomycosis. Thirty-three patients with onychomycosis in which the big toenail had a white band or spike were enrolled in this study. We drilled a hole about 3-mm-wide in the most proximal part of the white band or spike using a ball-shaped metal file and then, through the hole, sampled the underlying nail material softened by fungi after removing the superficial hard nail plate. Fungi in 32 (97.0%) of the nail samples were detected by direct KOH examination. When incubated on Sabouraud's dextrose agar slant with chloramphenicol and cycloheximide, fungal cultures were obtained from 27 (81.8%) of the 33 nail samples. Fourteen of the fungal isolates were identified as T. rubrum, 11 as T. mentagrophytes, and 2 as Acremonium sp. The nail drilling method is suitable for diagnosing onychomycosis with a white band or spike, because it gives a high isolation rate and leaves the patients' nail relatively more intact compared with other methods.     

甲真菌病的诊断和治疗进展

近年来甲真菌病的治疗取得了显著进展,一批高效安全的抗真菌药物问世,可供选择的药物和不同的疗程、不同的组合也在不断增多,通过广泛地临床应用对于疗效和安全性均积累了宝贵的经验。同时一些新型的非口服药物治疗方法也开始在临床上应用,为甲真菌病的治疗开辟了新的方向。我国于2008年制订了甲真菌病指南,并在此基础上不断进行深入解读和补充,以提高临床医师对于甲真菌病诊断的认识,     

New criteria for the laboratory diagnosis of nondermatophyte moulds in onychomycosis

Background  Nondermatophyte moulds (NDM) may be found as aetiological agents or as contaminants in onychomycosis. The classic and most used criteria for the diagnosis of NDM are those established by English in 1976.
Objectives  The aim of this article is to re-evaluate the laboratory criteria for the diagnosis of NDM in onychomycosis.
Patients and methods  Patients with suspected NDM of the nail underwent five consecutive examinations by both KOH and mycological culture; at the first visit, three samples from the affected nail were taken and were examined separately. Later those patients underwent four consecutive examinations; during this stage only a single sample for both KOH and culture was taken. We compared the culture results obtained from the three nail samples obtained at the first visit with the results from the four consecutive visits.
Results  We noted a clear trend showing that as the number of positive cultures increases (one to three cultures) during the first examination, the percentage of subsequent positive cultures, taken during the four consecutive visits, also increased.
Conclusions  We suggest that when NDM infection is found in the first culture, the patient should be re-examined in a subsequent visit in which three separate samples are taken from the affected nail. If NDM is confirmed in all three cultures, the diagnosis of NDM is established. Treatment should be recommended in patients who show positive results in all three cultures.     

甲真菌病诊治指南（2008年版）

中华医学会皮肤性病学分会真菌学组及国内相关知名专家反复讨论和修改,将甲真菌病诊疗指南成文如下,供国内同行参考.     

Polymerase chain reaction in the diagnosis of onychomycosis

Onychomycosis is a mycotic infection of the nail which accounts for 50% of all nail disorders. However, there is no predictably successful diagnostic approach to onychomycosis. The aim of this study was to demonstrate the feasibility of polymerase chain reaction (PCR) in diagnosis of onychomycosis and compare it with microscopy and culture. Fifty-two patients with clinically suspected onychomycosis were included in this study. After a sufficient amount of specimen was taken from the nail, PCR, microscopy and cultural methods were used in the examination of the samples. Out of all the 52 specimens, 40 (77%) specimens were positive by microscopy, 12 (23%) by culture, and 20 (38%) by PCR. In conclusion, if enough material can be taken, the PCR method appears to be a valuable diagnostic tool in cases where fungus can not be detected by conventional methods.