Unequivocal morphological diagnosis of fungi in morphologically abnormal nails.

AIMS: To analyse the prevalence of fungi in abnormal nails by morphological diagnosis. Prevalence studies of onychomycoses in temperate climate zones have yielded widely varying rates, possibly reflecting the confounding effects of referral bias, sampling specificity and intrinsic sensitivity of the diagnostic techniques employed.

METHODS AND

RESULTS

The method employed to identify fungi in nails entailed primary fixation using a non-formaldehyde-based coagulative fixative (BoonFix; Finetec, Japan) and microwave-enhanced processing to histology, followed by staining the paraffin sections with periodic acid-Schiff, using haematoxylin as a routine counterstain. The results of 990 nail samples were tabled for statistical analysis related to gender, patient age and diabetes mellitus status. In four of the 990 (< 1%) analysed cases the diagnosis was found to be equivocal using the method employed. These cases were jointly reviewed for definitive diagnosis. The overall prevalence of invasive hyphal structures was found to be 606/990 (approximately 61%). The relative risk for fungal infection in morphologically abnormal nails was found to be higher for persons < 20 years old or diabetic patients aged > or = 71 years.

CONCLUSIONS

The 61% positivity rate for fungi found justifies systematic direct submission of samples from abnormal nails for histological confirmation in order to avoid unwarranted treatment.