Clinico-aetiologic profile of Onychomycoses in a tertiary care centre in northeast India

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.

Correlation of clinical characteristics, by calculation of SCIO index, with the laboratory diagnosis of onychomycosis

INTRODUCTION

Onychomycosis is a chronic fungal infection with increasing incidence and the global prevalence is estimated to be 5.5%. The aim of our study was to perceive objectively severity of onychomycosis by calculating Scoring Clinical Index for Onychomycosis and to correlate this index with accurate laboratory diagnosis in our patients.

MATERIALS AND METHODS

The study population comprised of 417 patients with laboratory confirmed onychomycosis. For each patient, we recorded basic demographic information, site of infection, the most affected nail with onychomycosis, clinical presentation, and type of onychomycosis. The evaluation of the disease severity was based on Scoring Clinical Index for Onychomycosis which was calculated for every patient separately. Mycological identification was done by microscopy and fungal culture.

RESULTS

The majority of patients had distal and lateral subungual onychomycosis (95.44%) that was localized on big toe (62.59%), with female to male ratio 1.24:1. Male patients had significantly more nails affected with onychomycosis compared with female patients (p = 0.011), while female had significantly more often onychomycosis on fingernails 2-5 (p < 0.05), and they reported significantly more often pain (p < 0.05) and esthetic problems (p < 0.05). Mean Scoring Clinical Index for Onychomycosis was 16.76. Dermatophytes were most frequently isolated (91.85%). In patients with onychomycosis caused by dermatophytes, Scoring Clinical Index for Onychomycosis had significantly higher values (p = 0.032).

CONCLUSION

Comprehensive understanding of disease characteristics will allow introduction of individualized treatment plan for each patient, based on proper fungal identification and standardized method of evaluating disease severity, which could help the patient achieve a complete cure.