The Centor criteria are used to assess the probability of group A Streptococcus (GAS) pharyngitis in patients who present with a sore throat. These consist of the following four items:
2. Anterior cervical lymphadenopathy
3. Tonsillar exudate
4. Absence of cough
One point is added for each positive criterion. If the patient is under 15 years, a point should be added; or if they are over 44 years, a point should be subtracted.
A score of -1, 0, or 1 point indicates a <10% risk of GAS pharyngitis; cultures and antibiotic therapy are not indicated. Scores of 2 and 3 points indicate a risk of 15% and 32% respectively; cultures should be obtained and antibiotics started if they are positive.
A score of 4 points or above indicates a risk >50%. This mandates rapid strep testing and/or cultures; and antibiotics should be started empirically.
The classic features of infectious mononucleosis are fever, tonsillopharyngitis, lymphadenopathy, leukocytosis, and hepatosplenomegaly. These help in differentiating it from bacterial infections.
Skin eruptions are also common. These include maculopapular exanthems; morbilliform eruptions over the whole body; and in severe cases, erythroderma.
The occurrence of a transient generalized rash with maculopapular, petechial, or urticarial features in a patient who has been treated with penicillin to eradicate an ostensible group A Streptococcus infection is almost pathognomonic for infectious mononucleosis.
Other antibiotic classes have been implicated as well, but the penicillins are the most widely reported to produce this effect.
Infectious mononucleosis cannot be diagnosed on clinical grounds alone.
A common way to obtain laboratory confirmation is to use the monospot (heterophile antibody) test. However, a significant minority of patients do not develop heterophile antibodies. Furthermore, these antibodies are not specific to EBV, being encountered in other infections, autoimmune diseases, and malignancies. Last but not least, heterophile antibodies can persist for over a year and are therefore not always diagnostic of acute EBV infection.
Enzyme immunoassays for EBV-VCA IgM, EBV-VCA IgG, and EBNA-1 IgG are a better option. EBV-VCA IgM antibodies are seen in 75% of patients during acute illness. All patients eventually develop EBV-VCA IgG antibodies, allowing for documentation of previous infection. Last but not least, EBNA-1 antibodies are only detectable 90 days or longer after the onset of illness; their presence in a patient with acute symptoms rules out primary EBV infection.
Almost all patients with infectious mononucleosis experience some degree of splenomegaly. This is of clinical importance, as the enlarged soft spleen is highly susceptible to injury during this period.
In general, the progression of splenic enlargement is unpredictable. Ultrasound measurements are unreliable, as splenic size varies by person. That said, maximum enlargement is usually noted in the first 2 weeks of illness, although this may extend to as long as 3.5 weeks.
Splenic injury and/or rupture are rare but serious complications of infectious mononucleosis. They may occur spontaneously, or following seemingly trivial abdominal trauma. The majority of injuries occur within the first 21 days of illness; and they are exceedingly rare after 28 days.
Because of this, contact sports that place the chest or abdomen at risk for trauma should be avoided until this time period (i.e., 4 weeks) has passed. Activities that significant increase intra-abdominal pressure are also best avoided.
Currently, most authorities recommend that athletes with infectious mononucleosis should rest for 3 weeks, and then resume light activity. However, an earlier return to light activities such as walking and non-contact light aerobic exercises has not been shown to be deleterious.
As infectious mononucleosis carries the risk of persistent or chronic symptoms, most notably fatigue, the general consensus is that the athlete should be asymptomatic before returning to sports. However, waiting for resolution of laboratory abnormalities is not necessary.