Contemporary Tools for the Diagnosis and Management of Invasive Mycoses

The Glucatell (1-->3)- beta-D-glucan (BG) detection assay (Associates of Cape Cod) was studied as a diagnostic adjunct for invasive fungal infections (IFIs). On the basis of findings from a preliminary study of 30 candidemic subjects and 30 healthy adults, a serum BG level of >or=60 pg/mL was chosen as the cutoff. Testing was performed with serial serum samples obtained from 283 subjects with acute myeloid leukemia or myelodysplastic syndrome who were receiving antifungal prophylaxis. At least 1 serum sample was positive for BG at a median of 10 days before the clinical diagnosis in 100% of subjects with a proven or probable IFI. IFIs included candidiasis, fusariosis, trichosporonosis, and aspergillosis. Absence of a positive BG finding had a 100% negative predictive value, and the specificity of the test was 90% for a single positive test result and >or=96% for >or=2 sequential positive results. The Glucatell serum BG detection assay is highly sensitive and specific as a diagnostic adjunct for IFI.

Reported sensitivity of the galactomannan enzyme immunoassay as an early diagnostic test for invasive aspergillosis (IA) has been widely variable, ranging from 29% to 100% in earlier clinical studies. Studies performed to date have analyzed performance using per-patient calculations, limiting their ability to measure the impact of clinical variables that change over time, such as receipt of preventive antifungal therapy. In our study, performance of the test was calculated in per-patient and per-test analyses in a large cohort of patients at high risk for IA from 2 North American centers. A total of 272 serum samples obtained from 46 patients with IA and 3005 serum samples obtained from 269 control patients were analyzed using multiple index cutoff values to define positivity. Per-patient calculations yielded sensitivities of 43% and 70% using index cutoff values of 1.5 and 0.5, respectively; specificity decreased from 93% with use of the 1.5 index cutoff to 70% with use of the 0.5 index cutoff. Per-test calculations yielded sensitivities of 31% and 59% and specificities of 99% and 92% using index cutoff values of 1.5 and 0.5, respectively. Receipt of mold-active antifungal drugs on the day of testing decreased sensitivity; samples obtained from patients not receiving prophylactic or empirical antifungal drugs yielded a sensitivity of 89% and a specificity of 92% (with use of an index cutoff value of 0.5). These findings have direct implications for preventive strategies, because the diagnostic utility of the antigen assay is compromised during receipt of prophylactic or empirical antifungal therapies.

The term "aspergillosis" comprises several categories of infection: invasive aspergillosis; chronic necrotizing aspergillosis; aspergilloma, or fungus ball; and allergic bronchopulmonary aspergillosis. In 24 medical centers, we examined the impact of a culture positive for Aspergillus species on the diagnosis, risk factors, management, and outcome associated with these diseases. Most Aspergillus culture isolates from nonsterile body sites do not represent disease. However, for high-risk patients, such as allogeneic bone marrow transplant recipients (60%), persons with hematologic cancer (50%), and those with signs of neutropenia (60%) or malnutrition (30%), a positive culture result is associated with invasive disease. When such risk factors as human immunodeficiency virus infection (20%), solid-organ transplantation (20%), corticosteroid use (20%), or an underlying pulmonary disease (10%) are associated with a positive culture result, clinical judgment and better diagnostic tests are necessary. The management of invasive aspergillosis remains suboptimal: only 38% of patients are alive 3 months after diagnosis. Chronic necrotizing aspergillosis, aspergilloma, and allergic bronchopulmonary aspergillosis have variable management strategies and better short-term outcomes.