Are generic and original forms of piperacillin/tazobactam different in terms of false galactomannan test positivity?

Most common early diagnostic tool of IFI in high risk Hematology patients is galactomannan (GM) test. False positivity has beenobserved with TZP and other antibiotics. Widely usage of generic drugs has been continued owing to a significant cost advantageover original brand.The aim of this study is to compare the interaction of original and generic TZP formulations in terms of galactomannan test positivity.In January- February period, GM index was negative for all 35 patients who were receiving TZP. In that period, original TZP was usedfor patients in our institute.On the other hand, of 50 patients who were receiving TZP, GM index of 46 (92%) was above 0.5 in May. In that month, one typegeneric TZP was used for patients in our institute. Of the patients, 33 was male (66%), 27 were relapse diseases, 14 were newdiagnosis, and 9 were on remission. Allogeneic hematopoietic stem cell transplantation was performed in 9 and autologous HSCTin 12 patients. Fifteen patients were not neutropenic on GM test time. Thirty patients were receiving an antifungal agent whichwas including posaconazol in 10, fluconazole in 10, voriconazole in 8, and caspofungin in 2 patients pre GM test. In 13 (31.7%) of41 patients performed computed tomography (CT) scan, invasive fungal infection was supported by CT scan image. Moreover, therate of CT scan was more frequent (87% vs. 25%) in GM positive patients than those GM negative (p=0.016). This may lead moreunnecessary expenses of time and money. Mean GM positivity duration after beginning of TZP was 2.98±1.6 day, and mean GMnegativity time after discontinuation of TZP was 4.62±3.1 day.It was performed an analysis on GM levels of two generic and one original TZP. One of generic formulation had high GM levels(Figure 1).In conclusion, generic formulations of drugs are used in developing countries, but it should be cautious about unexpectedinteractions. High rate GM test positivity caused by generic formulation of TZP may lead unexpected high cost such as CT scan,maybe unnecessary antifungal treatment