title: Modified PAS stain: A new diagnostic method for onychomycosis.
abstract: BACKGROUND
  Onychomycosis is the most common nail disease and represents around 50% of nail disorders. Accurate diagnosis with adequate evidence is ideal before starting any treatment. Current diagnostic methods offer low specificity and sensitivity.
  
  
  OBJECTIVE
  To create a new method for the diagnosis of onychomycosis, and to compare its sensitivity and specificity with the existing methods.
  
  
  METHODS
  One hundred and ninety-two samples with clinical suspicion of onychomycosis were included and underwent modified PAS stain (M-PAS), KOH/chlorazol black (KOH/CB) and culture testing. Sensitivity, specificity, positive and negative predictive values were calculated.
  
  
  RESULTS
  In 152 out of 192 samples (79.2%) fungi structures were found in at least one of the three tests performed, and the patients were diagnosed with onychomycosis; 40 samples out of 192 (20.8%) were negative. Using M-PAS, filaments and/or spores were seen in 143 samples from the 152 positive (94%); 39 of them were negative to KOH/CB and positive to M-PAS (25.6%). With KOH/CB, filaments and/or spores were seen in 113 cases from the 152 positive samples (73.8% of the onychomycosis cases). Thirty-five cultures were positive, of which 77% were identified as Trichophyton rubrum; 117 onychomycosis cases were diagnosed despite the negative culture (76.9%). M-PAS showed 92.5% sensitivity and 55.55% specificity, a 67.5% positive predictive value and a 81.6% negative productive value.
  
  
  CONCLUSIONS
  This procedure, a combination of the existing methods to diagnose onychomycosis, KOH/CB together with a nail clipping biopsy, proved to have high sensitivity, as well as being rapid, easy, inexpensive and readily available in most hospital settings. M-PAS allowed us to diagnose 39 cases (25.6% of the cases of onychomycosis) that were false negative using only KOH/CB and culture.
authors.affiliation: Dermatology Resident, General Hospital "Dr. Manuel Gea González", Clazada de Tlalpan 4800, Sección XVI, CP 14080 México City, Mexico. Electronic address: hajar@ohsu.edu.
authors.forename: Tamar
authors.initials: T
authors.lastname: Hajar
authors.affiliation: Mycology Section Attending Physician, General Hospital "Dr. Manuel Gea González", Clazada de Tlalpan 4800, Sección XVI, CP 14080 México City, Mexico.
authors.forename: Ramon
authors.initials: R
authors.lastname: Fernández-Martínez
authors.affiliation: Mycology Section Attending Physician, General Hospital "Dr. Manuel Gea González", Clazada de Tlalpan 4800, Sección XVI, CP 14080 México City, Mexico.
authors.forename: Gabriela
authors.initials: G
authors.lastname: Moreno-Coutiño
authors.affiliation: Mycology Section Attending Physician, General Hospital "Dr. Manuel Gea González", Clazada de Tlalpan 4800, Sección XVI, CP 14080 México City, Mexico.
authors.forename: Elsa
authors.initials: E
authors.lastname: Vásquez Del Mercado
authors.affiliation: Head of the Mycology Section, General Hospital "Dr. Manuel Gea González", Clazada de Tlalpan 4800, Sección XVI, CP 14080 México City, Mexico.
authors.forename: Roberto
authors.initials: R
authors.lastname: Arenas
mesh_terms: D006801:Humans; D009172:Mycology / Q000379:methods; D014009:Onychomycosis / Q000175:diagnosis*; D012394:Rosaniline Dyes; D012680:Sensitivity and Specificity; D013194:Staining and Labeling
chemical_list: D012394:Rosaniline Dyes; C476677:Schiff's reagent
keywords: Diagnosis; Diagnóstico; Micología; Mycology; Onicomicosis; Onychomycosis