Ключевые слова: aged, analysis, analyzing, antigen, blood, blood analysis, blood test, cancer, catheter, checkup, chemical, chemistry, clinical, collection, control, detection, diagnosis, diagnostic, disease, doctor, elder, elderly, exam, free, free psa, gland, health, healthcare, hematology, hospital, illness, injection, lab, laboratory, man, marker, medical, medicine, needle, oncology, patient, prostate, prostate specific antigen, protein, psa, psa test, ratio, research, sample, screening, serum, specific, test, total, total psa, tube, tumor, tumor marker,