Recently, it has been proposed that frequent monitoring of EBV DNA loading by real-time PCR (TR-PCR) can be used as an early marker for deciding treatment in cases of active infection, especially when the rapid course is suspected of a VEB-ELP. Some case reports have shown that EBV DNA levels do not reach significant values despite the existence of active disease, so a close assessment should always be made based on the clinical condition.7-9. In addition to the problems of interpretation of the results of PCR-TR studies related to the clinical moment of the patient's infection, add different setbacks that must be faced in the laboratories, regarding the procedures of carrying out the study. There is variability in the results when laboratory tests already commercialized have been evaluated, compared to those carried out locally in each laboratory (homemade), sometimes by some differences in reagents used, denaturation temperature, etc. This requires the laboratories to verify the reproducibility of the tests, with inter-test and intra-test evaluations, with strict controls of the different variables and following the protocols established by the producing laboratories.