Analysis for chromosomal integration (ciHHV-6) is necessary to distinguish between ciHHV-6 and HHV-6 reactivation. When measuring DNA in the blood, levels of viral DNA are much higher with chromosomal integration, i.e., >6 log10 copies/ml, in whole blood. This compares to 1 copy per 104 to 105 leukocytes (3), i.e., ~2 log10 copies/ml in immunocompetent persons with latent, but not integrated HHV-6.1
Chromosomal integration is determined through qualitative HHV-6A and HHV-6B DNA PCR testing on hair follicles or nail clippings. Test results are reported as “detected” or “not detected.
1J Clin Microbiol. 2006 Apr; 44(4): 1571–1574.