To the Editor:
Epstein-Barr virus (EBV) is a human herpesvirus associated with B-cell lymphoproliferations occurring after solid organ and stem cell transplantation.1-4 In organ transplant recipients, the use of chronic immunosuppressive medications impairs T-cell surveillance of EBV-induced B-cell lymphoproliferations. Reversal of posttransplant lymphoproliferative disease (PTLD) has been reported after reduction in immune suppression.5 However, some disorders progress despite reducing or discontinuing these medications.2,6 The early detection of patients at risk for the development of PTLD may enable immunomodulation at an earlier point in the disease, thus facilitating successful treatment. Previous reports7 8 have demonstrated a correlation between high levels of EBV DNA and PTLD in organ transplant patients; however, a large cohort of patients has not been prospectively examined to determine the true positive predictive value of this assay. Although early detection of PTLD may improve outcome, it is not clear whether semiquantitative EBV DNA PCR is an appropriate screening tool for predicting which patients are at risk.
One hundred ninety-five patients returning to Indiana University Medical Center for post-organ transplantation follow-up had 5 mL of blood drawn in EDTA containing tubes for semiquantitative EBV PCR. The purpose of random screening with this assay was to obtain a baseline value in the event that signs or symptoms of PTLD developed at a later date. The number of patients by type of transplant was as follows: 165 liver transplants, 20 kidney transplants, 5 kidney and pancreas transplants, 4 kidney and liver transplants, and 1 heart transplant. All organ transplants were from a cadaveric source with the exception of 8 patients who received a kidney from a living related donor. All patients received either antithymocyte globulin at a dose of 15 mg/kg/d (Upjohn, Kalamazoo, MI) or OKT3 at 5 mg/d (Ortho Biotech, Raritan, NJ) for 7 to 10 days posttransplant in addition to methylprednisolone at 2 mg/kg/d. Patients also received azathioprine (1 to 3 mg/kg/d) and either cyclosporine A or FK 506. Patients with elevated levels of EBV DNA had follow-up levels obtained within 1 month.
Semiquantitative EBV PCR was performed on DNA extracted from patient white blood cells as previously described.9,10 Fisher’s exact test was used to examine the difference in distribution between elevated levels of EBV DNA based on pretransplant EBV serology and the presence or absence of PTLD. Associations between EBV DNA levels and patient age and serology were examined using logistic regression models.11
The mean age at the time of EBV PCR for these patients was 42.8 ± 18.7 years (range, 1 to 73 years), with a mean time posttransplant of 33 months (range, 1 to 236 months). Thirty patients were 18 years of age or younger, with 19 being less than 10 years of age. There was an association between both serology and age and having elevated levels of EBV DNA. Of the 136 patients who had pretransplant EBV titers performed, 15 were seronegative and 121 were seropositive. There was a higher percentage of EBV seronegative patients with elevated levels of EBV DNA (4 of 15 [26.7%]) compared with the percentage of EBV seropositive patients (3 of 121 [2.5%]) with elevated levels (P = .014). The mean age of patients with elevated EBV DNA was significantly lower than that of patients without elevated levels (12.6 v 39.1 years; P < .001).
Table 1 presents levels of EBV DNA in relation to the development of PTLD. All 3 patients who developed PTLD in this study had elevated levels of EBV DNA and were EBV seronegative pretransplant. The mean time posttransplant to the development of PTLD was 59 months (range, 52 to 67 months). Five of the 192 patients who did not develop PTLD had elevated levels at the time of screening. None of these 5 patients has developed PTLD or other signs of EBV infection, with a mean follow-up time of 6.4 months. Two of these five patients had levels of EBV DNA fall into the normal range. The 3 other patients with elevated levels of EBV DNA at initial screening had persistently elevated levels when checked 4, 6, and 8 months later, without clinical evidence of PTLD. The positive predictive value of this test in this patient population for the development of PTLD is 37.5%, and the negative predictive value is 100%.
Measuring EBV viral load in the peripheral blood has been postulated as one way of identifying organ transplant patients at risk for the development of PTLD, thereby providing the opportunity for altering immunosuppression when these tumors are more susceptible to immunomodulation. From previous studies, the incidence of PTLD has been shown to vary based on EBV serology pretransplant, the type of transplant, and the intensity of the immunosuppressive regimen used.3,12,13 Riddler et al7studied semiquantitative EBV PCR in solid organ transplant recipients and reported that all patients who developed PTLD in their study had a 2,000- to 10,000-fold elevation in EBV-infected peripheral blood lymphocytes. Kenagy et al8 have also demonstrated an increase in the levels of EBV DNA in organ transplant patients with PTLD. Savoie et al14 reported increased numbers of EBV-transformed cells in the peripheral blood of pediatric organ transplant patients in the first year posttransplant; however, only 2 of the 12 patients with elevated numbers of these cells developed PTLD. In the present report, the 3 patients with PTLD had elevated levels of EBV DNA, but 5 patients with ≥40,000 copies EBV/ μg DNA did not have any evidence of PTLD or EBV infection. Of note is the fact that the mean time posttransplant for patients in the present study was relatively late (33 months). This assay may have a higher correlation with the development of PTLD in patients who are earlier posttransplant, as has been reported in stem cell transplant patients.7 15 These data indicate that elevated levels of EBV DNA in the peripheral blood provide supportive evidence for PTLD in patients who have other signs of this disorder.
