The NEJM rarely covers HHV-6, but did an excellent case history of this patient with HHV-6 reactivation in conjunction with DRESS. The patient was not treated with an antiviral in spite of a plasma HHV-6 DNA load of 112,836, extensive lymphadenopathy, rash and abnormal liver function tests.
What did NEJM get wrong? They stated ciHHV6 could be ruled out because a) the viral load was only log 5 on a plasma DNA test and b) the viral load dropped to less than 500 copies/ml. The plasma viral load in a ciHHV-6 patient can fall below 500 copies/ml if the blood is centrifuged within a few hours. On the other hand, ciHHV-6 samples shipped overnight and centrifuged the next day, are reliably over 1,000 copies/ml. Whole blood but not plasma viral loads of >log 5.5 can be used to determine ciHHV-6 status in most cases.
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