American professional tennis player Andy Roddick, 27, has been wondering why his game has slipped this summer. The top ranked U.S., and former World No. 1 player has suffered a number of uncharacteristic losses. He felt more tired this summer, and couldn't keep up with his usual workout routine.
This Saturday, Roddick reported that one of several blood tests came back positive for mononucleosis. Doctors thought he had probably had the disease for a few months, and it was now nearly over. Roddick told the Associated Press:
"I'm just glad that we found out something that was causing it. It's weird, the fear of kind of the unknown and not knowing what's going on. There were some days where it was good, and some days where it was real bad. So it was like you would have one of those two or three good days, and it was like, 'OK, you're just being kind of a wimp.'"
"So it's nice to have a little bit of clarity moving forward. It's not something that's going to affect me, anything super-serious."
The Diagnosis of Mononucleosis
In most cases, the clinical diagnosis can be made from the characteristic triad of fever, pharyngitis, and lymphadenopathy lasting for 1 to 4 weeks. Blood work results include an elevated white blood cell count with an increased total number of lymphocytes, greater than 10% atypical lymphocytes, and a positive reaction to a "mono spot” or heterophile test. The combination of appropriate symptoms and characteristic lab work is diagnostic, and no further testing is necessary.
However, when the heterophile test results are negative, additional laboratory testing may be needed to differentiate EBV infections from mononucleosis-like illnesses caused by cytomegalovirus, adenovirus, or Toxoplasma gondii. As direct detection of EBV in blood is only available as a research tool, serologic testing is the method of choice for diagnosing primary infection.
Effective laboratory diagnosis can be made on a single acute-phase serum sample by testing for antibodies to several EBV-associated antigens simultaneously. In most cases, a distinction can be made as to whether a person is susceptible to EBV, has had a recent infection, has had infection in the past, or has a reactivated EBV infection.
An EBV panel of tests should include: IgM and IgG to the viral capsid antigen, IgM to the early antigen, and antibody to EBNA (EBV nuclear antigen).
IgM to the viral capsid antigen (VCA IgM) appears early in infection and disappears within 4 to 6 weeks.
IgG to the viral capsid antigen (VCA IgG) appears in the acute phase, peaks at 2 to 4 weeks after onset, declines slightly, and then persists for life.
IgG to the early antigen (EA IgG) appears in the acute phase and generally falls to undetectable levels after 3 to 6 months. Although in many people, detection of antibody to the early antigen is a sign of active infection, 20% of healthy people may have this antibody for years.
Antibody to EBNA is not seen in the acute phase, but slowly appears 2 to 4 months after onset, and persists for life.
Summary of interpretation: (Thanks to the CDC.)
The diagnosis of EBV infection is summarized as follows:
Susceptibility
If antibodies to the viral capsid antigen are not detected, the patient is susceptible to EBV infection.
Primary Infection
Primary EBV infection is indicated if IgM antibody to the viral capsid antigen is present and antibody to EBV nuclear antigen, or EBNA, is absent. A rising or high IgG antibody to the viral capsid antigen and negative antibody to EBNA after at least 4 weeks of illness is also strongly suggestive of primary infection. In addition, 80% of patients with active EBV infection produce antibody to early antigen.
Past Infection
If antibodies to both the viral capsid antigen and EBNA are present, then past infection (from 4 to 6 months to years earlier) is indicated. Since 95% of adults have been infected with EBV, most adults will show antibodies to EBV from infection years earlier. High or elevated antibody levels may be present for years and are not diagnostic of recent infection.
Reactivation
In the presence of antibodies to EBNA, an elevation of antibodies to early antigen suggests reactivation. However, when EBV antibody to the early antigen test is present, this result does not automatically indicate that a patient's current medical condition is caused by EBV. A number of healthy people with no symptoms have antibodies to the EBV early antigen for years after their initial EBV infection. Many times reactivation occurs subclinically.
Chronic EBV Infection
Reliable laboratory evidence for continued active EBV infection is very seldom found in patients who have been ill for more than 4 months. When the illness lasts more than 6 months, it should be investigated to see if other causes of chronic illness or CFS are present.