Usefulness of nail plate sample in the diagnosis of onychomycosis
Keywords:
Diagnosis, onychomycosis, nailsAbstract
Introduction: The sensitivity of conventional tests (direct-culture) for the diagnosis of onychomycosis (25-80%) represents a problem for the dermatologist’s therapeutic decision.
Objective: To determine the diagnostic accuracy of the nail plate sample in patients with clinical diagnosis of onychomycosis.
Methodology: Prospective study of diagnostic tests in 50 patients with suspected onychomycosis. The nail plate sample was taken with sterile nail clippers from the onycholysis area for mycological testing (KOH-culture) and histopathology (HE-PAS). Another sample by scraping debris from the ungueal bed was taken for mycological test. Sample collection and processing of the tests were performed in reference laboratories and interpreted blindly and independently. The debris from the ungueal bed was considered the gold standard.
Results: Feet were involved in 90% of patients, 86.6% with involvement of the hallux. The mycological test positivity was 80% for detritus, fungal structures were found by direct in 72% and in 64% were isolated by culture. In nail plate sample, the sensitivity was 87.5% and specificity was 80%, the positive likelihood ratio was 4,4. Five samples that were positive for PAS staining were negative in the gold standard test. Net sensitivity increased to 95% by analysis of parallel testing of nail plate. Most of the isolates were Candida species (77,3% in debris and 75,9% in nail plate), C. parapsilosis being the most commonly isolated.
Conclusion: We propose the nail plate sample for mycological test and PAS staining, in addition to the sample of debris for the diagnosis of onychomycosis.
Author Biographies
Luz Marina Gómez
Médica dermatóloga; jefe, Servicio de Dermatología, Escuela de Ciencias de la Salud; coordinadora, Grupo de Investigación en Dermatología; profesora titular, Universidad Pontificia Bolivariana; dermatóloga, Clínica SOMA, Medellín, Colombia
Mónica Massaro
Médica, M.Sc. en Epidemiología; profesora asociada, Escuela de Ciencias de la Salud, Universidad Pontificia Bolivariana e Instituto Neurológico de Antioquia. Medellín, Colombia
Ángela María Tabares
Licenciada en Bacteriología y Laboratorio Clínico, Grupo de Micología Médica y Experimental, Corporación para Investigaciones Biológicas; Escuela de Microbiología, Universidad de Antioquia; Escuela de Ciencias de la Salud, Universidad Pontificia Bolivariana, Medellín, Colombia
Alejandra Zuluaga
Médica, microbióloga clínica, Grupo de Micología Médica y Experimental, Corporación para Investigaciones Biológicas; Escuela de Microbiología, Universidad de Antioquia; Escuela de Ciencias de la Salud, Universidad Pontificia Bolivariana, Medellín, Colombia
Juan David Vélez
Médico, Universidad Pontificia Bolivariana, Medellín, Colombia
Alejandro Vélez
Médico patólogo; docente, Escuela de Ciencias de la Salud, Universidad Pontificia Bolivariana; Hospital Pablo Tobón Uribe, Medellín, Colombia
Margarita Jaramillo
Bacterióloga, Laboratorio de Patología, Escuela de Ciencias de la Salud, Universidad Pontificia Bolivariana, Medellín, Colombia
Luz Elena Cano
Ph.D. en Inmunología, Grupo de Micología Médica y Experimental, Corporación para Investigaciones Biológicas; Escuela de Microbiología, Universidad de Antioquia; Escuela de Ciencias de la Salud, Universidad Pontificia Bolivariana, Medellín, Colombia
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