title: Cost-effectiveness of diagnostic tests for toenail onychomycosis: a repeated-measure, single-blinded, cross-sectional evaluation of 7 diagnostic tests.
abstract: OBJECTIVE
  Our purpose was to estimate and compare the cost-effectiveness of the most commonly used diagnostic tests for onychomycosis: potassium hydroxide preparation (KOH), interpreted both by a dermatologist (KOH-CLINIC) and a laboratory technician (KOH-LAB); KOH with dimethyl sulfoxide (KOH-DMSO) and with chlorazol black E (KOH-CBE), interpreted by a dermatologist; culture using dermatophyte test medium, culture with Mycobiotic and Inhibitory Mold Agar (Cx); and histopathologic analysis using periodic acid-Schiff stain (PAS).
  
  
  METHODS
  This was a repeated-measure, blinded, cross-sectional study conducted at the Minneapolis Veterans Affairs Medical Center. Inclusion criteria included: at least one toenail with 25% or more clinical disease, which was defined as subungual debris with onycholysis and/or onychauxis. Exclusion criteria included other nail dystrophies, use of oral antifungal medication for 2 months or longer within the past year, or topical ciclopirox lacquer within 6 weeks of enrollment. The main outcome measure was the cost-effectiveness (Medicare and non-Medicare costs) of 7 diagnostic tests. Sensitivity (at least 3 positive tests) was the unit of effectiveness.
  
  
  RESULTS
  Two hundred four participants were enrolled; their average age was 69.5 years and 95.5% were male. PAS was the most sensitive test (98.8%); it was statistically significantly more sensitive than all other diagnostic tests except KOH-CBE (94.3%). Dermatophye test medium was the least sensitive test (57.3%). KOH-CBE was statistically significantly more cost effective than any other test, with the exception of KOH-CLINIC and KOH-LAB. PAS was the least cost effective.
  
  
  CONCLUSIONS
  Test specificities were not evaluated.
  
  
  CONCLUSIONS
  KOH-CBE should be the test of choice for practitioners confident in interpreting KOH preparations because of its combination of high sensitivity and cost-effectiveness.
authors.affiliation: University of Minnesota, Minneapolis, Minnesota, USA.
authors.forename: Kia K
authors.initials: KK
authors.lastname: Lilly
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Koshnick
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Grill
authors.forename: Zena M
authors.initials: ZM
authors.lastname: Khalil
authors.forename: David B
authors.initials: DB
authors.lastname: Nelson
authors.forename: Erin M
authors.initials: EM
authors.lastname: Warshaw
mesh_terms: D000368:Aged; D003362:Cost-Benefit Analysis; D003430:Cross-Sectional Studies; D003955:Diagnostic Tests, Routine / Q000191:economics / Q000379:methods; D005260:Female; D005533:Foot Dermatoses / Q000175:diagnosis* / Q000191:economics*; D006801:Humans; D008297:Male; D014009:Onychomycosis / Q000175:diagnosis* / Q000191:economics*; D012680:Sensitivity and Specificity; D016037:Single-Blind Method