ABSTRACT
Introduction Ten percent potassium hydroxide examination is one of the most frequently performed tests in dermatology. It is usually supplemented by fungal culture for detection of superficial fungal infection of the skin and its appendages. We aim to determine the predictive values of 10% potassium hydroxide examination in Sarawak General Hospital. Materials and Methods A retrospective review of 292 skin scraping results for 10% potassium hydroxide examination and culture was done between October 2003 and December 2004. Data for all the scrapings were analysed for predictive values, specificity, sensitivity and likelihood ratio with fungal culture as the gold standard investigation. Separate data analysis was done for those with onychomycosis. Results Positive cultures were noted in 80.8% of skin scrapping cases and 85.4% of onychomycosis cases. For the skin scrapping cases, the positive predictive value of 10% potassium hydroxide examination was 67.4%, negative predictive value of 16.9%, sensitivity of 12.3% and specificity of 75%. For those with onychomycosis, the positive predictive value was 75%, negative predictive value 13.6%, specificity 85.7% and sensitivity was 7.3%. The positive likelihood ratio for all cases and onychomycosis cases was 0.5 whereas the negative likelihood ratio was 0.9. Conclusion Ten percent potassium hydroxide examination has a very low negative predictive value and sensitivity, making it a poor investigative tool in Sarawak General Hospital. Thus, culture of the skin scraping for suspected superficial fungal infection of the skin and its appendages is of utmost importance. Steps to improve the quality of 10% potassium hydroxide examination are important as it is an easy and inexpensive test.