Case report: false positive elevated serum‐galactomannan levels after autologous hematopoietic stem cell transplantation caused by oral nutritional supplements

Immunocompromised patients are at high risk for invasive fungal infections (IFI) like invasive pulmonary aspergillosis. Detection of galactomannan (GM) levels in the serum has been found to be a valid surrogate parameter for early diagnosis of IFI. Nevertheless, several clinical circumstances may influence serum GM levels. Here, we present a 68‐year old male patient with an angioimmunoblastic T cell lymphoma with aberrant expression of CD20 who was admitted for high‐dose chemotherapy with consecutive autologous stem cell transplantation. Initial laboratory tests did not show any significant abnormalities. High‐dose chemotherapy containing rituximab, thiotepa, etoposide, cytarabine, and melphalan (R‐TEAM) was administered and autologous stem cells were retransfused without any problems. During the neutropenic phase, the patient developed severe mucositis, presenting as persistent diarrhea (CTC‐grade 3) and diminished appetite. He consumed several energy drinks per day as nutritional supplements. Routinely performed serum tests showed a GM level of 1.5 (norm < 0.5). CT scans showed no signs of IFI. A calculated antifungal therapy was initiated. However, during the course of neutropenia and after engraftment the GM levels increased without any signs of IFI. Testing for GM in the energy drinks revealed a high positive result for GM. Hence, the patient was advised to stop consuming these drinks and the GM level decreased and normalized eventually. The same drink given to individuals without mucositis did not lead to an increase in GM levels. We thus assume a disturbed intestinal mucosal barrier because of the treatment‐induced diarrhea as a cause of false positive GM results. This case report indicates a potential source of false positive results for serum GM tests. Energy drinks can be an important support in the diet of hematologic patients. A disturbed intestinal mucosal barrier may lead to the transfer of ingested sugar‐molecules into the patients' blood and thereby affect serum GM levels. Immunocompromised patients are at risk for opportunistic infections like invasive fungal infections (IFI), invasive aspergillosis (IA), or invasive candidiasis (IC). Furthermore, underlying hematologic malignancies or intensive chemotherapy regimens often make invasive diagnostic procedures impossible 1. Fungal cell wall components like aspergillus galactomannan (GM) or candida mannan (CM) can be found in the patients' blood in the case of IFI 2, 3, 4, 5. Hence, they have been found to be a good surrogate parameter for early diagnosis of IFI and immediate preemptive antifungal therapy. Current guidelines recommend performing serum‐galactomannan tests at least twice a week in patients at risk of invasive fungal infections 6. In contrast, several studies suggest potential causes for false‐positive GM tests. Enteral supplemental nutrition might be a source for positive test results in the condition of allogeneic stem cell transplantation and intestinal graft versus host disease 7, 8, 9, 10. Our case suggests a potential enteral cause of false‐positive serum‐GM tests in the context of autologous stem cell transplantation and therapy‐induced mucositis.