Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry: a new tool in diagnostic investigation of nail disorders?

Diagnosing Onychomycosis: What’s New?

An overview of the long-established methods of diagnosing onychomycosis (potassium hydroxide testing, fungal culture, and histopathological examination) is provided followed by an outline of other diagnostic methods currently in use or under development. These methods generally use one of two diagnostic techniques: visual identification of infection (fungal elements or onychomycosis signs) or organism identification (typing of fungal genus/species). Visual diagnosis (dermoscopy, optical coherence tomography, confocal microscopy, UV fluorescence excitation) provides clinical evidence of infection, but may be limited by lack of organism information when treatment decisions are needed. The organism identification methods (lateral flow techniques, polymerase chain reaction, MALDI-TOF mass spectroscopy and Raman spectroscopy) seek to provide faster and more reliable identification than standard fungal culture methods. Additionally, artificial intelligence methods are being applied to assist with visual identification, with good success. Despite being considered the ‘gold standard’ for diagnosis, clinicians are generally well aware that the established methods have many limitations for diagnosis. The new techniques seek to augment established methods, but also have advantages and disadvantages relative to their diagnostic use. It remains to be seen which of the newer methods will become more widely used for diagnosis of onychomycosis. Clinicians need to be aware of the limitations of diagnostic utility calculations as well, and look beyond the numbers to assess which techniques will provide the best options for patient assessment and management.

Infrared spectroscopy as a novel tool to diagnose onychomycosis

BACKGROUND

The determination of causative organisms of onychomycosis is still not optimal. There remains a need for a cheap, fast and easy-to-perform diagnostic tool with a high capacity to distinguish between organisms.

OBJECTIVES

To determine whether attenuated total-reflectance Fourier transform infrared (ATR-FTIR) spectroscopy can detect and differentiate causative agents in culture-based, ex vivo nail and in vivo nail models.

METHODS

A methodological study was conducted. Both the ex vivo nail model and in vivo pilot study were carried out in an academic university hospital.

RESULTS

Analysis of cultured fungi revealed spectral differences for dermatophytes (1692-1606 and 1044-1004 cm^-1 ) and nondermatophytes and yeasts (973-937 cm^-1 ), confirmed by dendrograms showing an excellent separation between samples from different genera or species. Exploration of dermatophytes, nondermatophytes and yeasts growing on ex vivo nails exposed prominent differences from 1200 to 900 cm^-1 . Prediction models resulted in a 96·9% accurate classification of uninfected nails and nails infected with dermatophytes, nondermatophytes and yeasts. Overall correct classification rates of 91·0%, 97·7% and 98·6% were obtained for discrimination between dermatophyte, nondermatophyte and yeast genera or species, respectively. Spectra of in vivo infected and uninfected nails also revealed distinct spectral differences (3000-2811 cm^-1 , 1043-950 cm^-1 and 1676-1553 cm^-1 ), illustrated by two main clusters (uninfected vs. infected) on a dendrogram.

CONCLUSIONS

Our data suggest that ATR-FTIR spectroscopy may be a promising, fast and accurate method to determine onychomycosis, including identification of the causative organism, bypassing the need for lengthy fungal cultures.

Quantitative mass spectrometry of unconventional human biological matrices

The development of sensitive and versatile mass spectrometric methodology has fuelled interest in the analysis of metabolites and drugs in unconventional biological specimens. Here, we discuss the analysis of eight human matrices-hair, nail, breath, saliva, tears, meibum, nasal mucus and skin excretions (including sweat)-by mass spectrometry (MS). The use of such specimens brings a number of advantages, the most important being non-invasive sampling, the limited risk of adulteration and the ability to obtain information that complements blood and urine tests. The most often studied matrices are hair, breath and saliva. This review primarily focuses on endogenous (e.g. potential biomarkers, hormones) and exogenous (e.g. drugs, environmental contaminants) small molecules. The majority of analytical methods used chromatographic separation prior to MS; however, such a hyphenated methodology greatly limits analytical throughput. On the other hand, the mass spectrometric methods that exclude chromatographic separation are fast but suffer from matrix interferences. To enable development of quantitative assays for unconventional matrices, it is desirable to standardize the protocols for the analysis of each specimen and create appropriate certified reference materials. Overcoming these challenges will make analysis of unconventional human biological matrices more common in a clinical setting.This article is part of the themed issue 'Quantitative mass spectrometry'.

Clinical Trial Study in the Treatment of Nail Psoriasis with Pulsed Dye Laser

Abstract Objective: The treatment options for nail psoriasis have been limited, and the management of nail psoriasis has been challenging for physicians. This study aimed at evaluating the effect of different pulse durations in the treatment of nail psoriasis with the 595-nm PDL to determine the optimal pulse duration. Methods: Forty patients with bilateral fingernail psoriasis were recruited and completed a 6-month trial. PDL was applied on the proximal and lateral nailfolds based on random assignment. Eghity nails were treated with 6-millisecond pulse duration and 9 J/cm(2) whereas 80 nails were treated with 0.45-millisecond pulse duration and 6 J/cm(2). Nail Psoriasis Severity Index (NAPSI) was used to assess the clinical outcome from pretreatment and posttreatment photographs. Results: After 6 months of first treatment, there was a significant reduction in overall NAPSI, nail matrix NAPSI, and nail bed NAPSI scores from baseline in both groups; however, no significant difference was found between the two pulse duration groups. Side effects were mild including transient petechiae and hyperpigmentation. Conclusion: Both the longer 6-millisecond and shorter 0.45-millisecond pulses of PDL (595 nm) have been clinically proven to be effective for the treatment of nail matrix and nail bed psoriasis.

Onychomycosis: modern diagnostic and treatment approaches

The medical term onychomycosis should be understood as chronic infection of the nails caused by a fungus. The most common causative agents are the dermatophytes and Candida species. The less common are certain types of moulds (nondermatophyte moulds or NDMs). In approximately 60-80 % of the cases, onychomycosis is due to dermatophytes. Among dermatophytes, the most often isolated causative pathogen is Trichophyton (T.) rubrum. Other common species are T. interdigitale (formerly T. mentagrophytes), Epidermophyton floccosum, and T. tonsurans. The most significant yeasts causing onychomycosis are Candida albicans and Candida parapsilosis. Predisposing factors for onychomycosis include mainly diseases such as diabetes mellitus, peripheral vascular arterial disease, chronic venous insufficiency, polyneuropathies of diverse etiologies, and immunosuppression, e.g., myeloproliferative diseases (such as lymphoma and paraproteinemia), HIV/AIDS, etc. Other factors facilitating the fungal infection are frequent trauma in professional sportsmen, often accompanied by excessive perspiration. The diagnostic methods that are often applied in different dermatologic departments and ambulatory units are also different. This precludes the creation of a unified diagnostic algorithm that could be used everywhere as a possible standard. In most of the cases, the method of choice depends on the specialist's individual experience. The therapeutic approach depends mostly on the fungal organism identified by the dermatologist or mycologist. This review hereby includes the conventional as well as the newest and most reliable and modern methods used for the identification of the pathogens causing onychomycosis. Moreover, detailed information is suggested, about the choice of therapeutic scheme in case whether dermatophytes, moulds, or yeasts have been identified as causative agents. A thorough discussion of the schemes and duration of the antifungal therapy in certain groups of patients have been included.

Laboratory diagnostics of invasive fungal infections: an overview with emphasis on molecular approach

Although invasive fungal diseases (IFDs) are relatively rare, they have become an increasingly common life-threatening complication in a variety of critically ill patients. Due to changes in treatment strategies, patterns of IFDs have changed substantially as well. Yeast infections have shifted toward a higher proportion of non-albicans Candida species, but their overall incidence has remained stable. In contrast, IFDs caused by molds, including particularly various species of Aspergillus, Fusarium, and Mucorales, have increased in number. In view of the growing incidence and the high mortality rates of IFDs, accurate diagnostic techniques permitting timely onset of adequate antifungal treatment are of paramount importance. Although conventional approaches such as microscopy, cultivation, histopathological examination, and imaging methods still represent the gold standard, the diagnosis remains difficult because of limited sensitivity and specificity. Noninvasive and culture-independent diagnostic techniques, including fungal antigen detection, and different molecular-based techniques are becoming increasingly important. Of the fungal surrogate markers such as cell wall components, galactomannan and (1,3)-β-D-glucan by commercially available diagnostic kits have become widely used, but the results are still controversial. A plethora of PCR-based diagnostic methods targeting different gene regions and exploiting a variety of amplicon detection tools have been published. Molecular assays have the capacity to overcome the limitations of other diagnostic approaches, but the current lack of methodological standardization and validation, together with not always clear interpretation of the results, has prevented broad application in the clinical setting.

MALDI-TOF-mass spectrometry applications in clinical microbiology

MALDI-TOF-mass spectrometry (MS) has been successfully adapted for the routine identification of microorganisms in clinical microbiology laboratories in the past 10 years. This revolutionary technique allows for easier and faster diagnosis of human pathogens than conventional phenotypic and molecular identification methods, with unquestionable reliability and cost–effectiveness. This article will review the application of MALDI-TOF-MS tools in routine clinical diagnosis, including the identification of bacteria at the species, subspecies, strain and lineage levels, and the identification of bacterial toxins and antibiotic-resistance type. We will also discuss the application of MALDI-TOF-MS tools in the identification of Archaea, eukaryotes and viruses. Pathogenic identification from colony-cultured, blood-cultured, urine and environmental samples is also reviewed.