The utility of plasma polymerase chain reaction for human herpes virus-6 among pediatric bone marrow transplant recipients: results of a pilot study

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Abstract
We evaluated the utility of plasma polymerase chain reaction (PCR) for surveillance of human herpes virus 6 (HHV-6) infection among pediatric bone marrow transplant (BMT) recipients. We used a prospective, non-interventional design involving a study group and controls. BMT recipients and healthy controls were evaluated. BMT subjects had HHV-6 PCR done biweekly for 12 weeks post transplantation, while a single PCR test was done on controls. For the PCR assay, EDTA blood was collected and DNA extracted from whole blood and cell-free plasma using standard procedures. The PCR was first performed on DNA from whole blood and if a positive result was obtained, the test was repeated on the DNA from the plasma. Thirty BMT recipients (13 autologous and 17 allogeneic) were enrolled, on whom a total of 156 PCR tests were performed, while six tests were done on six healthy controls. The median age of BMT subjects was 6.2 years (range 0.5–17.5 years). The median age of the control subjects was 6.6 years (range 2–10 years). Among asymptomatic BMT patients who had PCR surveillance, the positivity rate was 3.3% (1/30) on whole blood and 0% (0/30) on plasma. None of the six healthy subjects had a positive PCR test on whole blood. During the period of the surveillance study, 14 patients had diagnostic evaluations for HHV-6 disease because of clinical symptoms. Two of these patients were diagnosed with disease associated with HHV-6 (graft failure and encephalitis) and had positive PCR tests on whole blood and plasma and whole blood and cerebrospinal fluid, respectively. We conclude that despite the fact that HHV-6 seropositivity rates are high among children, the frequency of HHV-6 plasma PCR positivity is low in pediatric BMT subjects who are asymptomatic for HHV-6 disease. Given that a positive test on plasma is consistent with active infection, this increases the utility of the PCR test as a diagnostic aid in evaluating syndromes presumed to be due to HHV-6 in pediatric bone marrow transplant recipients. Bone Marrow Transplantation (2001) 28, 473–477.