Diagnosis and management of cases of suspected dermatomycosis in The Netherlands: influence of general practice based potassium hydroxide testing.
BACKGROUND
Microscopy of a potassium hydroxide preparation of skin scrapings or nail clippings, although widely advocated as a test for dermatomycosis, is used in only a small proportion of cases.


OBJECTIVE
This study set out to investigate the effect of potassium hydroxide testing on the subjectively assessed probability that a dermatomycosis was present.


METHODS
The study was undertaken in 1992 in Limburg, a province in the south of the Netherlands. Ten general practitioners and eight trainees completed a questionnaire and performed a potassium hydroxide preparation for each patient presenting with a skin condition that they thought might be caused by dermatomycosis. Skin or nail material was also sent to a microbiology laboratory where another potassium hydroxide preparation as well as a culture were performed, these two tests serving as a gold standard against which to judge the potassium hydroxide preparation by the general practitioners. Data from a total of 164 cases were analysed.


RESULTS
The results of the potassium hydroxide test carried out in the practice had a considerable influence on the subjectively assessed probability that a dermatomycosis was present, especially if the outcome was positive. The indication for antifungal treatment was altered as a result of the test in a quarter of all cases, mostly from negative to positive. Use of the practice potassium hydroxide test could increase the proportion of correct therapeutic decisions from 54% to 69%, with 20% of cases being undertreated. Of cases that gave a positive test result in the practice 83% also had a positive laboratory test result, while of cases that gave a negative practice result 43% were positive in the laboratory.


CONCLUSIONS
The potassium hydroxide test improves the diagnostic process in cases of possible dermatomycosis and may result in a change in management. The test can provide a confirmation of the diagnosis of dermatomycosis but is not useful in the exclusion of this diagnosis.
De Kock
C A
CA
University of Limburg, Maastricht, Netherlands.
Sampers
G H
GH
Knottnerus
J A
JA
D019411:Clinical Laboratory Techniques; D003881:Dermatomycoses / Q000175:diagnosis*; D003937:Diagnosis, Differential; D005069:Evaluation Studies as Topic; D005194:Family Practice; D006801:Humans; D006878:Hydroxides; D009426:Netherlands; D017680:Potassium Compounds
D006878:Hydroxides; D017680:Potassium Compounds; C029943:potassium hydroxide