Sorted By Test Name - Mayo Medical Laboratories

HHV6
87532
hCG is synthesized by the cells of the placenta and is involved in maintaining the corpus luteum during
pregnancy. It is detected as early as 1 week after conception. The diagnostic cutoff for pregnancy is >25
IU/L. In pregnancy, the levels of hCG increase exponentially for about 8 to 10 weeks after the last
menstrual cycle. Later in pregnancy, about 12 weeks after conception, the concentration of hCG begins to
fall. Other sources of elevated hCG values include ectopic pregnancy, threatened abortion, microabortion,
recent termination of pregnancy, gestational trophoblastic disease, choriocarcinoma, and some germ cell
tumors.
Useful For: Diagnosing pregnancy Investigation of suspected ectopic pregnancy Monitoring in vitro
fertilization patients
Interpretation: Values between 5 and 25 IU/L are indeterminate for pregnancy. Consider confirming
with repeat test in 72 hours. Values in pregnancy should double every 3 days for the first 6 weeks. Both
normal and ectopic pregnancies generally yield positive results of pregnancy tests. The comparison of
quantitative human chorionic gonadotropin (hCG) measurements with the results of transvaginal
ultrasonography (TVUS) may aid in the diagnosis of ectopic pregnancy. When an embryo is first large
enough for the gestation sac to be visible on TVUS, the patient generally will have hCG concentrations
between 1,000 and 2,000 IU/L. (These are literature values. Definitive values for this method have not
been established at this time.) If the hCG value is this high and no sac is visible in the uterus, ectopic
pregnancy is suggested. Elevated values will also be seen with choriocarcinoma and hydatiform mole.
Reference Values:
Negative: 25 IU/L
Suggest repeat testing of indeterminate results in 72 hours.
Clinical References: Snyder JA, Haymond S, Parvin CA, et al: Diagnostic considerations in the
measurement of human chorionic gonadotropin in aging women. Clin Chem 2005;51:1830-1835
Human Herpesvirus-6, Molecular Detection, PCR, Plasma
Clinical Information: Herpesvirus-6 (HHV-6) is a member of the Herpesviridae family. These
viruses contain DNA surrounded by a lipid envelope. Among members of this group, this virus is most
closely related to cytomegalovirus (CMV) and HHV-7. As with other members of the herpesvirus group
(herpes simplex virus [HSV] 1, HSV 2, varicella zoster virus [VZV], CMV, Epstein-Barr virus [EBV],
HHV-7, HHV-8), HHV-6 may cause primary and reactivated infections subsequent to latent association
with cells.(1) Infection with HHV-6 occurs early in childhood. Most adults (80%-90%) have been
infected with this virus. HHV-6 was first linked with exanthem subitum (roseola infantum) in 1998; since
then, the virus has been associated with central nervous system disease almost exclusively in
immunocompromised patients.(1) HHV-6 is commonly detected in patients posttransplantation. Clinical
symptoms associated with this viral infection include febrile illness, pneumonitis, hepatitis, encephalitis,
and bone marrow suppression. However, the majority of HHV-6 infections are asymptomatic.(2) The
incidence of HHV-7 infection and its clinical manifestations post-transplantation are less well
characterized. HHV-6 is designated as variant A (HHV-6A) or variant B (HH6-B) depending on
restriction enzyme digestion patterns and on its reaction with monoclonal antibodies. Generally, variant B
has been associated with exanthem subitum, whereas variant A has been found in many
immunosuppressed patients.(3)
Useful For: As an adjunct in the rapid diagnosis of human herpesvirus-6 infection
Interpretation: A positive result indicates the presence of specific DNA from human human
herpesvirus-6 (HHV-6) and supports the diagnosis of infection with this virus. A negative result indicates
the absence of detectable DNA from HHV-6 in the specimen, but it does not negate the presence of
organism or active or recent disease.
Reference Values:
Not applicable
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