Patients must meet the accepted criteria for CRS, which includes 12 weeks of paranasal inflammation. This diagnosis is strengthened by abnormal radiographic findings. The study of choice is a limited sinus CT scan with coronal cuts, which may demonstrate mucosal thickening and air-fluid levels. Greater than 8 mm of mucoperiosteal thickening is considered abnormal. In contrast to AFS, these patients do not necessarily have elevated fungal-specific IgE or positive skin testing for fungal antigens.

Successful fungal cultures have been greatly enhanced by new techniques that first release fungal hyphae from nasal mucin. Pretreatment with dithiothreitol frees the organisms by breaking sulfur hydrogen bonds. Specific histologic stains, including Gomori methenamine silver stain and fluorescein-labeled chitinase stain, have enabled selective visualization of fungal organisms (11). Using these techniques, Ponikau has identified fungus in nearly all of his patients with CRS (1).

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