Comparison of Diagnostic Methods: in the Evaluation of Onychomycosis

Objective: Onychomycosis is common nail problem, accounting for up to half of all nail diseases. Onychomycosis requires administration of antifungal agent for long period. So many nail disorders may mimic the onychomycosis clinicaly. Therefore sensitive, quick and inexpensive test is essential for screening nail specimens. Traditional methods used for the diagnosis of onychomycosis have been fungal nail culture and KOH preparation of nail samples. But recently, It has been reported that KONCPA (KOH treated Nail clipping + PAS) test might be a useful complementary method with high positive rate and excellent view for making the diagnosis of onychomycosis. The aim of this study was to compare culture, KOH preparation, calcofluor white stain (CFW), and KONCPA in the diagnosis of onychomycosis and to determine their sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV). Materials and Methods: In the cross-sectional study, nail speciemens were collected from 101 patients suspected to onychomycosis during 14 months, Nail speciemens were examined by potassium hydroxide 20%, KONCPA, calcofluor white stain and culturing on Sabouraud's dextrose agar containing chloramphenicol (SC), Sabouraud's dextrose agar containing cyclohexamide and chloramphenicol (SCC). Culture was chosen as the gold standard for statistical analysis. Results: Of the patients, 100 had at least 1 of the 4 diagnostic methods positive for the presence of organisms. The following were calculated for each test: sensitivity; specificity; positive predictive value; and negative predictive value. The positive rates of fungal culture, KOH preparation, CFW and KONCPA were 74.2%, 85.1%, 91.09%, and 99.01%, respectively. The sensitivities of each of the techniques were as follows: KOH 92%; CFW 96%; and KONCPA 100%. KONCPA method were more sensitive than KOH preparation (p=0.0002) and CFW (P = 0.008). The specificities were as follows: KOH 38%; CFW 23%; and KONCPA 3.8%. The positive predictive value calculated for the different techniques were: KOH 81%; CFW 78%; and KONCPA 75%. In terms of negative predictive value, the results were: KOH 66%; CFW 66%; and KONCPA 100%. Conclusion: KONCPA was the most sensitive among the tests. It is also superior to the other methods in its negative predictive value. It was easy to perform, rapid, gave significantly higher rates of detection of onychomycosis compared to the standard methods, namely KOH mount and mycological culture and