In vitro tests : how do they influence therapeutic choices?

In an era in which invasive opportunistic fungal infections, especially aspergillosis and candidiasis, have become one of the major causes of morbidity and mortality in patients with hematological disorders and malignancies, clinicians can benefit from the growing role that laboratories play in the early diagnosis and therapeutic management of such infections. In particular, in vitro testing results, if the methods used are reliable and reproducible, can be useful either for specific therapeutic approaches or for detecting antifungal drug resistance. Although the title of our review implies answers to the question on how in vitro tests can influence the therapeutic choice of an antifungal drug, we prefer that the reader forms his own judgement. To help readers to form their judgement, this review will be focused on: descriptions of the current available methods for in vitro antifungal susceptibility testing of yeasts and moulds; summary on what has been done in the correlation of in vitro susceptibility results with the clinical outcome of human or experimental fungal infections following specific therapy with a defined antifungal drug; discussion on the appropriateness of the routine use of in vitro antifungal susceptibility testing, the potential clinical application of its results; and, finally, assessment of the clinical relevance of in vitro detection of antifungal drug resistance.