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 68year old male patient with an angioimmunoblastic t cell lymphoma with aberrant expression of cd20 who was admitted for highdose chemotherapy with consecutive autologous stem cell transplantation . highdose chemotherapy containing rituximab , thiotepa , etoposide , cytarabine , and melphalan ( rteam ) was administered and autologous stem cells were retransfused without any problems . during the neutropenic phase , the patient developed severe mucositis , presenting as persistent diarrhea ( ctcgrade 3 ) and diminished appetite . routinely performed serum tests showed a gm level of 1.5 ( norm < 0.5 ) . 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 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 treatmentinduced diarrhea as a cause of false positive gm results . this case report indicates a potential source of false positive results for serum gm tests . a disturbed intestinal mucosal barrier may lead to the transfer of ingested sugarmolecules 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 , 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 serumgalactomannan tests at least twice a week in patients at risk of invasive fungal infections 6 . 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 falsepositive serumgm tests in the context of autologous stem cell transplantation and therapyinduced mucositis . a 69year old male patient was electively admitted to our hospital for highdose chemotherapy and autologous stem cell transplantation . on admission , no clinical signs of infection ( like fever , coughing , sneezing , or dysuria ) had occurred in the weeks prior to admission . nine months earlier a rare variant of an angioimmunoblastic tcell nonhodgkin lymphoma with aberrant expression of cd20stage ivb had been diagnosed . after diagnosis , an immunochemotherapy with six cycles of the rchopprotocol ( rituximab , cyclophosphamide , doxorubicine , vincristin , prednisolone ) and two consolidating cycles of rituximab had been administered . the first cycle of chemotherapy had been complicated by acute renal failure due to tumor lysis , a central venous line infection and a stomatitis due to reactivation of herpes simplex virus . a restaging examination after six cycles of chemotherapy showed a good partial remission , thus , consolidation with highdose chemotherapy and autologous stem cell transplantation was planned . since diagnosis routine laboratory testing showed no noticeable problems except from slightly elevated serumcreatinine levels and the diagnostic workup was unremarkable apart from arterial hypertension . after excluding potential contraindications , we administered a myeloablative chemotherapy following the rteamprotocol ( rituximab , thiotepa , etoposide , cytarabine , and melphalan ) 11 . on the day of stem cell retransfusion , the patient developed severe diarrhea ( ctcgrade 3 ) most probably caused by chemotherapy 12 . thus , the diarrhea was assumed to be chemotherapy induced and hypercaloric drinks were offered to the patient because of weight loss and reduced appetite . the patient consumed one to three of these drinks per day . on the day of stem cell retransfusion , elevated body temperatures could be measured and fever occurred from day + 2 until day + 9 after stem cell transplantation , and was accompanied by an increase in the creactive protein ( the clinical course after the stem cell transplantation is depicted in fig . blood cultures indicated a central line infection with staphylococcus epidermidis , thus , antibiotic treatment with teicoplanin was initiated . also , stool cultures showed the presence of multiresistant e. coli and meropenem was added . repeatedly performed routinetests for serumgalactomannan showed a marked elevation after the period of neutropenia , after resolution of fever and despite decreasing levels of creactive protein ( see fig . gm levels were tested using the platelia aspergillus ag kit ( biorad ) and candidaantigen levels using the platelia candida ag plus kit ( biorad laboratories gmbh , munich , germany ) . because of a suspected invasive aspergillosis , a calculated antifungal therapy with voriconazole was initiated although ctimaging showed no signs of invasive pulmonary fungal infection . for further investigation of the inconsistent findings regarding the positive serum aspergillusgm tests and the missing clinical evidence for an invasive aspergillosis , the patients ' environment was examined . the consumed hypercaloric drinks were tested with the same diagnostic fungal tests as for the patients ' blood samples . both , aspergillusgm and candidaantigen could be detected in high levels ( 5.35 and 700 pg / ml , respectively ) . in order to test for accuracy , two healthy volunteers consumed the same drinks and blood samples at baseline and 4 h after the ingestion of the drink were tested for aspergillusgm . as expected , the tests showed negative results throughout . the patient was advised to stop the consumption of the drinks and serumgm levels decreased ( see fig . serumgalactomannan levels were normal and ctimaging still showed no signs of invasive pulmonary fungal infection . trends of creactive protein ( trianglesymbols and solid line ) and serumgalactomannan ( dots and broken line ) after stem cell retransfusion : the creactive protein levels increased with fever in neutropenia and normalized after initiation of an effective antibacterial therapy ; the level of serumgalactomannan increased even after neutropenic reconstitution ( on day 12 ) and fell after advising the patient to quit consuming the hypercaloric drinks . malnutrition and weight loss are frequent complications of highdose conditioning and autologous peripheral blood stem cell transplant and supportive enteral nutrition might be beneficial 13 . in the presented case , the patient received highcaloric drinks containing galactooligosaccharides as well as gluconate , which has been reported to cause elevated galactomannan levels 14 . the food industry uses complex sugar molecules like galactomannans for stabilizing and thickening of many products 15 . , they might affect diagnostic procedures in case of passing over from the intestine into the bloodstream . it should also be kept in mind , that galactomannan levels in blood can be elevated due to intravenous antibiotic administration . occurrence of aspergillusgm in the blood is thought to be caused by angioinvasion of growing aspergillus hyphae . the most widely used biomarker for invasive aspergillosis is an eiabased procedure and uses a monoclonal antibody for the detection of the 15 glactofuranose side chain of the galactomannan molecule ( biorad , platelia aspergillus ag kit ) . although positivity of the biomarkers preceded clinical signs of ifi in several cases , a drawback is the rate of falsepositive results in up to 15% 17 , 18 . diarrhea is one of the most commonly occurring side effects of chemotherapy and may indicate a dysfunction in the intestinal mucosal barrier . the team conditioning protocol contains melphalan , which is known to be a potential cause of severe diarrhea as a known side effect 19 . we hypothesize that the dysfunction of the intestinal mucosal barrier in the context of stem cell transplantation was the reason for the falsepositive serumgalactomannan results . several case reports about different falsepositive aspergillus tests were published in the setting of allogenic stem cell transplantation and graftversushost disease . to the best of our knowledge there are no reports about falsepositive gmtests in recipients of autologous stem cell transplantation due to enteral supplemental nutrition agents . in addition , we tested the drinks and the patients ' serum for candida mannan ( biorad , platelia , candida ag plus ) . while the drink was tested positive , candida antigen could not be detected in the patient 's serum . we assume a different intestinal processing and absorption of the antigens in the context of chemotherapyassociated disturbed mucosal barrier function . diagnosis of invasive fungal infection remains a challenge for clinicians , especially in the context of stem cell transplantation . surrogate parameters like antigen detection in the patients ' serum are an essential diagnostic element . test results should be critically interpreted in the clinical context with respect to potential causes of falsepositive findings in order to prevent unnecessary antimycotic treatment . in our case ' , aspergillusgm but not candidaantigen could be detected in the patients ' blood , whereas both molecules could be detected in the potential source of the falsepositive test results . thus , the exact mechanisms of disturbed intestinal barrier function as a cause for falsepositive findings in the context of stem cell transplantation remain unclear .
key clinical messagepositive galactomannan tests in patients who underwent chemotherapy without any clinical signs of a fungal infection should lead the clinician to consideration of a falsepositive test result . 
 oral nutritional supplements may be a cause , especially in the case of concomitant disturbance of the gastrointestinal mucosal barrier because of mucositis .