Widely Available Blood Tests Enhance Diagnostic Sensitivity of Fungal Infections

Diagnosing these infections in a timely and accurate manner is tough, largely because the current method—using punch biopsies for tissue culture and histology—yields unreliable results with only about a 10% match rate. Now, a new study has found that the use of newer tests can improve the diagnosis of this time-sensitive condition.

In the study, researchers at Thomas Jefferson University (Philadelphia, PA, USA) found that two commonly available serum marker blood tests, galactomannan and 1,2-beta-D-glucan, were capable of improving diagnostic sensitivity in IFI cases. The first test, serum galactomannan (GM), is a polysaccharide antigen present specifically in the cell walls of Aspergillus fungi. According to the study, this test is effective for diagnosing invasive aspergillosis, showing a sensitivity range of 63% to 78% and a specificity range of 85% to 93%. A unique advantage of GM is its ability to distinguish between aspergillosis and mucormycosis. However, the researchers have cautioned that the test's sensitivity may decrease if the patient is already undergoing systemic antifungal therapy, particularly mold-active agents.

The second test, 1,2-beta-D-glucan (BDG), is a component found in the cell walls of a range of fungi, including Candida, Aspergillus, and Pneumocystis jirovecii. As many fungi contain BDG, the test is more useful for broadly identifying the presence of fungal etiology rather than specific causative agents. Past meta-analyses have shown that BDG can distinguish between probable and unlikely IFIs with a sensitivity of 77% and a specificity of 85%. However, dermatologists need to be aware that this test can yield false positives, as it does not differentiate between various fungal species. Hence, it may not be suitable for patients with a low likelihood of having an IFI, suggests the study. The researchers have recommended that dermatologists use these blood tests alongside traditional histopathology and cultures to enhance diagnostic sensitivity.

“A double negative GM and BDG can lower the probability of an IFI and encourage providers to seek alternative diagnoses,” stated the researchers.

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