Infectious complications and the utility of serum and cellular markers of infections in the setting of allogeneic hematopoietic stem cell transplantation.

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients are severely immunocompromised and susceptible to bacterial, viral, and fungal infections. Despite improved anti-microbial prophylaxis and preemptive strategies, bacterial bloodstream infections (BSIs) occur frequently in allo-HSCT recipients and are associated with increased morbidity and mortality. Cytomegalovirus (CMV) and Epstein Barr virus (EBV) are the most relevant viruses following allo-HSCT and remain major concerns. Fungal infections, including those caused by Candida and Aspergillus species, are persistent and feared complications. We aim to provide clinicians caring for allo-HSCT recipients with a comprehensive overview of the risk factors that predispose patients to common bacterial, fungal, and viral infections during the first years post-transplant. The focus is on the value of noninvasive diagnostic biomarkers and serological assays in enhancing the early detection and management of these infections. Effective management of infectious complications following allo-HSCT relies on continuous immune recovery monitoring and the implementation of advanced diagnostic methods. Utilizing noninvasive diagnostic methods is crucial for early detection and different intervention strategies. The development and integration of reliable microbiological markers into clinical practice is essential for enhancing patient outcomes and mitigating infection-related risks. Emphasizing diagnostic innovation will be pivotal in advancing patient care post-allo-HSCT.