The study protocol was approved by the hospital ethics committee (contract number 183/25.06.2020). Patients agreed to participate in this study with the use of their medical **data** for scientific purposes. All patients signed the informed consent. Twenty patients, four who were systematic healthy and sixteen with leukemia (ALL, AML, CLL, CML), non-smoking, without periodontal disease, and a mean age of 55.3 years, were recruited from the Department of Hematology, Institute of Oncology "Ion Chiricuta", Cluj-Napoca, Romania. For saliva sampling, each patient was seated in a relaxed position, with their head bent forward in order to allow saliva to accumulate in the anterior region of the oral cavity. Firstly, patients were instructed not to eat and drink liquids for 2 h, not to use lipstick/lip balm, chewing gum, before the saliva was collected. Secondly, the patient swallowed, and then saliva was collected in a polypropylene tube; during sampling, the patient was asked to avoid swallowing. After collection, the samples were stored at 4 • C and then were stored at −80 • C until the analysis.