(1-3)-β-D-Glucan (Fungitell) Test

Fungal infections that reach your bloodstream or organs are among the most dangerous and underdiagnosed threats in medicine. Blood cultures, the traditional way to catch these infections, can take days or even weeks to turn positive, and roughly half the time they never do. That delay costs lives. BDG ((1,3)-beta-D-glucan) is a molecule that leaks from fungal cell walls into your blood when fungi invade deep tissues, and testing for it can flag an infection days to weeks before cultures come back.

This is not a test you order for general wellness screening. BDG testing is designed for people who are immunocompromised or critically ill and at genuine risk of invasive fungal disease. If that describes your situation, or if your medical team suspects a deep fungal infection, understanding this test can help you advocate for faster diagnosis and earlier treatment.

What This Test Actually Detects

BDG is a large sugar molecule (a polysaccharide) built from chains of glucose. It forms a major structural piece of the cell walls of many fungi, including Candida species, Aspergillus species, and Pneumocystis jirovecii (a fungus that causes a specific type of pneumonia in people with weakened immune systems). When these fungi invade your tissues, their cell walls break apart and release BDG into your bloodstream. The Fungitell assay detects this circulating BDG in a blood sample.

Two fungi are blind spots for this test. Cryptococcus species and the fungi that cause mucormycosis (a group called Mucorales) do not release enough BDG to be detected reliably. If your medical team suspects either of these infections, they will need different diagnostic tools.

How Accurate Is the Test?

Across multiple large studies and meta-analyses, the Fungitell assay catches about 75% to 80% of invasive Candida infections and correctly rules out infection about 80% of the time. For invasive aspergillosis in people with blood cancers, sensitivity ranges from 73% to 89% depending on the threshold used. A Cochrane review, however, found enormous variability across individual studies, with sensitivity ranging from 27% to 100% and specificity from 0% to 100%. That range tells you this is a test whose accuracy depends heavily on context: who is being tested, what infection is suspected, and what threshold the lab uses.

For rarer invasive mold infections, the numbers hold up reasonably well. One meta-analysis found 76.7% sensitivity for invasive fusariosis and 81.5% for invasive scedosporiosis, with BDG turning positive before conventional diagnosis in 73% and 94% of those cases, respectively.

Mortality Risk in Critically Ill People

Elevated BDG levels carry prognostic weight even beyond fungal infection. In a study of 453 mechanically ventilated patients who did not have invasive fungal disease, those with BDG at or above 40 pg/mL were roughly 3 times as likely to belong to a hyperinflammatory subtype (a pattern of heightened immune activation) and had higher 30-day mortality. The likely explanation is that BDG leaks into the blood through a damaged gut lining, a phenomenon called fungal translocation, where fragments of gut fungi cross a weakened intestinal barrier and provoke widespread inflammation.

Among patients after major abdominal surgery, BDG above 100 pg/mL was associated with 39.0% mortality compared to 13.7% in those at or below 100 pg/mL. Strikingly, 37.3% of those with elevated BDG died even without confirmed invasive candidiasis, suggesting the test captures something about systemic stress or gut barrier breakdown that goes beyond fungal infection alone.

Liver Disease and Gut Barrier Breakdown

People with cirrhosis (severe liver scarring) often have damaged gut linings that allow fungal fragments to cross into the blood. A pilot study of 70 patients with cirrhosis found that those with positive BDG results had roughly 6.8 times the mortality risk compared to those with negative results, even after adjusting for other factors. BDG levels also tracked closely with markers of immune activation, suggesting this test may reflect the degree to which a damaged liver and leaky gut are driving chronic inflammation.

Coronary Plaque in People with HIV

One cross-sectional study of 93 people with HIV on antiretroviral therapy examined whether BDG levels relate to hidden heart disease visible on CT scans. BDG levels showed a modest but statistically significant correlation with total coronary plaque volume. This is preliminary evidence from a single study in a specific population, and no prospective trials have confirmed whether BDG predicts heart attacks or strokes. But it reinforces the idea that BDG may be a marker of chronic low-grade fungal translocation through a compromised gut, which could contribute to arterial inflammation over time.

Interpreting Your Results

The Fungitell assay uses 80 pg/mL as its standard cutoff for a positive result. Anything below this is considered negative. However, research suggests the optimal cutoff may depend on the clinical situation. One meta-analysis found that 60 pg/mL provided the best overall accuracy when tested against strict diagnostic criteria. In ICU patients with suspected invasive candidiasis, 50 pg/mL performed best.

These thresholds apply specifically to the Fungitell assay. Other commercial assays (Wako, Fungitec-G, Glucatell) use different cutoffs and are not interchangeable. Always compare your results within the same assay over time.

When Results Can Be Misleading

False positives are the single biggest limitation of this test, especially in hospitalized patients. If you see a positive result, it does not automatically mean you have a fungal infection. Several common medical situations can push BDG above the cutoff without any fungi being involved.

Certain intravenous antibiotics, including some cephalosporins, carbapenems, and ampicillin-sulbactam, can cause elevated readings. So can receiving intravenous immunoglobulin (IVIG), therapeutic antibodies, or albumin infusions. In one study of hematology-oncology patients receiving immunoglobulins or therapeutic antibodies, the false-positive rate was high enough to be a significant clinical problem. The chemotherapy agent pegylated asparaginase is another known culprit.

Hemodialysis can raise BDG levels, particularly with older cellulose-based dialysis membranes, which pushed median levels from 9.4 to 332 pg/mL in one study. Modern synthetic membranes (polysulfone, polymethyl methacrylate) do not cause this problem. Roughly 22% of hemodialysis patients show BDG above 80 pg/mL without any infection.

Recent abdominal surgery is another major confounder. Between 54% and 61% of patients tested positive during intestinal procedures, with 12% to 17% remaining positive 4 to 5 days afterward, all without fungal infection. Bacterial bloodstream infections (especially gram-negative bacteria, with a 59% false-positive rate in one study), gastrointestinal mucosal damage, and exposure to surgical gauze containing glucan can also trigger false results.

One reassuring finding: eating foods rich in beta-glucan (such as mushrooms or oats) does not raise your blood levels. A pilot trial gave participants a high-dose oral beta-glucan challenge and found no change in blood BDG levels up to 8 hours later, whether in healthy people, people with HIV, or those with advanced liver disease.

Tracking Your Trend

A single BDG reading is far less useful than a series of results tracked over time. The Infectious Diseases Society of America recommends requiring consecutive positive results rather than acting on a single positive, because specificity improves substantially with serial testing. In one analysis, requiring two consecutive positive results raised specificity to 78%, though sensitivity dropped to 65%. The tradeoff is worth it in most situations, because the cost of treating a false positive (unnecessary antifungal drugs, their side effects, and their expense) is high.

For people at ongoing risk, such as those with blood cancers or stem cell transplants who are not receiving antifungal prophylaxis, twice-weekly screening allows early detection. BDG can turn positive a median of 5 to 6 days before blood cultures in surgical ICU patients at risk for abdominal candidiasis. Once antifungal treatment begins, falling BDG levels are a good sign. In patients with invasive candidiasis, a downward trajectory had a 90% positive predictive value for treatment success, while persistently rising levels suggested treatment failure.

BDG kinetics differ by infection type. In candidemia, levels often begin dropping within days of effective treatment, with 65.7% of patients showing dropped or normalized values by discharge. In invasive aspergillosis, the decline is much slower: the median one-week decrease was 0 pg/mL in one study of 69 patients, and most still had levels above 80 pg/mL at 6 and 12 weeks. For aspergillosis, do not rely on BDG alone to judge whether treatment is working.

How This Test Compares to Galactomannan

Galactomannan is the other major blood test for invasive fungal infections, but the two tests have different strengths. Galactomannan is specific to Aspergillus, meaning a positive result points directly at that pathogen. BDG is a pan-fungal marker that picks up Candida, Aspergillus, Pneumocystis, Fusarium, and others, but cannot tell you which one. A 2024 meta-analysis found galactomannan had 53% sensitivity and 94% specificity for invasive aspergillosis, compared to BDG's 72% sensitivity and 82% specificity. Combined testing achieved 84% sensitivity and 76% specificity, outperforming either test alone.

If the clinical question is specifically about Aspergillus, galactomannan is the more targeted choice. If the question is broader (could this be any invasive fungal infection?), BDG casts a wider net. In practice, many infectious disease specialists order both.