Clinical diagnosis - Aspergillus and Aspergillosis

Most fungal infections are not distinctive in their clinical features, although a few are (Table). The clinical features of each are described in each section for each fungal disease.

Highly distinctive fungal infections that may require confirmation by laboratory testing

Disease	Fungus	Comment
Oral thrush	Candida albicans	May be fluconazole resistant, if previously treated
Seborrheic dermatitis and dandruff	Malassezia furfur	Highly distinctive clinical appearance
Chromomycosis	Multiple	Diagnosis clearcut but different fungi involved
Ringworm	Multiple	Appearance not always distinctive, especially if steroid cream used, and some fungi are un-responsive to terbinafine and acquired from infected pets.
Athlete’s foot	Trichophyton rubrum orinterdigitale	If limited to the toewebs, really distinctive, May be co-infected with bacteria.

Of the 5 groups of fungal infections, the most difficult to diagnose are the serious infections. These same infections usually have no symptoms or non-specific features (ie mimicking a bacterial chest infection), and it only when the fungal disease worsens that testing is initiated. As many as 40% of fatal life-threatening fungal infections are not even considered before death, with testing or treatment given. Corticosteroids mask fever and symptoms and topical steroids mask rash features.

Fungal infections that can be diagnosed with one test with or without imaging;

Disease	Key test	Comment
Vaginal thrush	Microscopy showing yeasts and hyphae or chromogenic	Commonest misdiagnosis in bacterial vaginosis, but several others
Eosophageal candidiasis	Upper GI endoscopy or barium swallow	Endoscopy preferable, culture taken through scope confirms species and antifungal sensitivity
Candida bloodstream infection	Blood culture	Several species involved; not more than 75% sensitive and dependent on how much blood is cultured
Onychomycosis (nail infection)	Microscopy showing hyphae	In toenail infection, the causative fungus important to determine therapy. Cultures desirable.
Tinea capitis	Hair microscopy showing hyphae	The causative fungus important to optimise therapy. Cultures desirable.
Otitis externa	Microscopy or culture showing Aspergillus(usually A. niger)	Main differential diagnosis is bacterial infection,Pseudomonas especially
Allergic bronchopulmonary aspergillosis (video)	Serum IgE >1,000 KIU/L in context of asthma or cystic fibrosis	Specific fungal skin or IgE tests useful, as are eosinophil count and chest CT scan.
Severe asthma with fungal sensitization (SAFS) (video)	Specific anti fungal IgE levels, and raised total IgE	Anti fungal IgE as tested by specific skin testing.
Fungus ball of the sinus	CT or MR scan of the sinuses	Highly characteristic appearance, culture and histopathology follow surgical cure.
Chronic pulmonary aspergillosis (video)	Aspergillus IgG in context of upper lobe cavitation on chest Xray or CT scan	Presence of fungal ball in a cavity very typical, but only present in 25%. Most caused by Aspergillus fumigatus.
Pneumocystis pneumonia	Positive microscopy or PCR test in context of AIDS or other immunocompromised patient	Low level positive PCR can be problematic to interpret.
Cryptococcal meningitis	CSF showing yeasts with a capsule or cryptococcal antigen test	Blood cryptococcal antigen test an excellent screen, but some false negatives.