Nonculture diagnostic methods for invasive fungal infections

Abstract

Nonculture methods are useful when diagnosing several systemic or invasive mycoses. Commercially available methods include immunoassays to detect cell wall or capsular polysaccharides; zymogen-based colorimetric assays to detect (13)-beta-D-glucan, another cell wall polysaccharide; and molecular methods to detect fungal DNA. Molecular diagnostic methods have received much attention in the last decade but their accuracy has not been established, in part because of a lack of standardized, commercially available reagents or test kits. Serologic tests for antibodies are useful for diagnosis of histoplasmosis and coccidioidomycosis.

Isolated Pancreatic Histoplasmosis: An Unusual Suspect of Pancreatic Head Mass in an Immunocompetent Host

“…9,10 Immunocompromised hosts, on the other hand, are more likely to have higher fungal burden with positive antigen tests and culture results and a negative serology. 6,11 Itraconazole is considered the treatment of choice in noncritically ill patients with histoplasmosis. 12 However, gastric acid is required for adequate absorption of itraconazole pills and hence could not be used in this case owing to prior Roux-en-Y gastric bypass.…”

Diagnosis and management of histoplasmosis

“…Complement fixation (CF) antibody tests for the yeast and mycelial antigens and assessment for h and m precipitin bands on the immunodiffusion assay are most useful in nonimmunocompromised patients who have been ill for more than 1 month. The sensitivity of these serology tests is 78% to 89% for localized pulmonary infection, 40% to 80% for acute pneumonia with diffuse infiltrates, 90% for chronic pulmonary histoplasmosis, and 60% to 80% for disseminated histoplasmosis [8]. Serology titers peak approximately 4 to 6 weeks after infection and often are negative earlier in the course of illness [8], emphasizing the need to obtain paired acute and convalescent specimens.…”

“…The sensitivity of these serology tests is 78% to 89% for localized pulmonary infection, 40% to 80% for acute pneumonia with diffuse infiltrates, 90% for chronic pulmonary histoplasmosis, and 60% to 80% for disseminated histoplasmosis [8]. Serology titers peak approximately 4 to 6 weeks after infection and often are negative earlier in the course of illness [8], emphasizing the need to obtain paired acute and convalescent specimens. Higher titers of CF antibodies correlate with severity of infection in adolescents [5].…”

“…Higher titers of CF antibodies correlate with severity of infection in adolescents [5]. False-positive CF titers are attributed to prior asymptomatic infection in endemic areas; serology studies remain positive for several years after acute infection [8]. Up to 40% of immunosuppressed patients with documented histoplasmosis do not mount a measurable antibody response, limiting the value of serologic testing in this patient population [7••].…”

“…Antigen can be detected in urine, serum, cerebrospinal fluid (CSF), or BAL [8]. The firstgeneration antigen assay, initially reported in 1986, was a radioimmunoassay, which had excellent performance characteristics for disseminated histoplasmosis [10] but was less accurate for diagnosing other forms of the infection.…”