title: Clinical diagnosis of toenail onychomycosis is possible in some patients: cross-sectional diagnostic study and development of a diagnostic rule.
abstract: BACKGROUND
  Suspected toenail onychomycosis is a frequent problem. Clinical diagnosis has been considered inadequate.
  
  
  OBJECTIVE
  To assess the diagnostic accuracy of clinical findings for detecting fungi in toenails, and to develop and validate a clinical diagnostic rule aimed at improving dermatologists' diagnosis of onychomycosis.
  
  
  METHODS
  A cross-sectional diagnostic study was performed including a total of 277 patients seen by 12 dermatologists. The gold standard was the presence of dermatophytes on culture or a positive nail plate biopsy. For each sign we described prevalence, sensitivity, specificity, positive and negative predictive values, and likelihood ratios for positive and negative results. We developed a diagnostic clinical rule and validated it in a subsample.
  
  
  RESULTS
  Helpful findings to predict the presence of fungi are: previous diagnosis of fungal disease; abnormal plantar desquamation (affecting > 25% of the sole); onychomycosis considered the most probable diagnosis by a dermatologist; and presence of interdigital tinea. When dermatologists considered onychomycosis the most probable diagnosis and plantar desquamation was present (13% of patients), the positive predictive value for presence of fungi was 81%. When both signs were absent (34% of patients), the positive predictive value for absence of fungi was 71%. In other situations, clinical diagnosis might not give enough information to decide on therapy.
  
  
  CONCLUSIONS
  In 13% of the patients (a large number in absolute terms), when dermatologists consider onychomycosis the most probable diagnosis and plantar desquamation is present, therapy should be started without any further test, as clinical diagnosis is at least as accurate as laboratory tests. In other situations, an optimal management strategy should be defined.
authors.affiliation: Department of Dermatology, Complexo Hospitalario de Pontevedra, SERGAS, LoureiroCrespo, 2, Pontevedra 36001, Spain. ignacio.garcia.doval@sergas.es
authors.forename: I
authors.initials: I
authors.lastname: Garcia-Doval
authors.forename: F
authors.initials: F
authors.lastname: Cabo
authors.forename: B
authors.initials: B
authors.lastname: Monteagudo
authors.forename: J
authors.initials: J
authors.lastname: Alvarez
authors.forename: M
authors.initials: M
authors.lastname: Ginarte
authors.forename: M X
authors.initials: MX
authors.lastname: Rodríguez-Alvarez
authors.forename: M T
authors.initials: MT
authors.lastname: Abalde
authors.forename: M L
authors.initials: ML
authors.lastname: Fernández
authors.forename: F
authors.initials: F
authors.lastname: Allegue
authors.forename: L
authors.initials: L
authors.lastname: Pérez-Pérez
authors.forename: A
authors.initials: A
authors.lastname: Flórez
authors.forename: M
authors.initials: M
authors.lastname: Cabanillas
authors.forename: G
authors.initials: G
authors.lastname: Peón
authors.forename: A
authors.initials: A
authors.lastname: Zulaica
authors.forename: J
authors.initials: J
authors.lastname: Del Pozo
authors.forename: P
authors.initials: P
authors.lastname: Gomez-Centeno
mesh_terms: D000328:Adult; D000368:Aged; D003883:Arthrodermataceae / Q000302:isolation & purification; D001706:Biopsy; D004812:Epidemiologic Methods; D005260:Female; D005533:Foot Dermatoses / Q000175:diagnosis* / Q000209:etiology / Q000473:pathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009262:Nails / Q000473:pathology; D014009:Onychomycosis / Q000175:diagnosis* / Q000209:etiology / Q000473:pathology; D010808:Physical Examination