infectious diseases
Infectious Mononucleosis
Diagnosis of Infectious Mononucleosis
Heterophile antibody test Sometimes EBV serologic testing Infectious mononucleosis should be suspected in patients with typical symptoms and signs. Exudative pharyngitis, anterior cervical lymphadenopathy, and fever may be clinically indistinguishable from those caused by Streptococcal Infections . However, posterior cervical or generalized adenopathy or hepatosplenomegaly suggests infectious mononucleosis. Moreover, detection of streptococci in the oropharynx does not exclude infectious mononucleosis. Primary Human Immunodeficiency Virus (HIV) Infection can produce a clinical picture resembling acute EBV infection. If patients have risk factors for HIV infection, the following should be done: Quantitative HIV RNA viral load in blood Combination antibody immunoassay and p24 antigen assay HIV enzyme-linked immunosorbent assay (ELISA)/Western blot is usually negative during the acute infection and thus should not be used alone to diagnose early primary HIV infection. Quantitative HIV RNA and p24 antigen detection are more sensitive for diagnosing acute HIV infection because HIV RNA and p24 antigen are present in blood before HIV antibodies develop. Primary HIV infection can resemble acute EBV infection; patients with risk factors for HIV infection should be tested using quantitative HIV RNA viral load in blood, combination antibody immunoassay and p24 antigen testing. Cytomegalovirus (CMV) Infection (CMV) may also cause a mononucleosis syndrome, with atypical lymphocytosis as well as hepatosplenomegaly and hepatitis but usually not with severe pharyngitis. Toxoplasmosis may cause a syndrome similar to infectious mononucleosis with fever and lymphadenopathy but usually not with pharyngitis. Laboratory diagnosis usually involves a complete blood count and EBV serologic testing. Lymphocytes that are morphologically atypical account for up to 30% of the white blood cells. Although individual lymphocytes may resemble leukemic lymphocytes, lymphocytes are heterogeneous, which is unlikely in Overview of Leukemia . Atypical lymphocytes may also be present in Two serologic tests are used to diagnose acute EBV infection: Heterophile antibody testing Specific EBV antibody testing Heterophile antibodiesare measured using various agglutination card (monospot) tests. However, heterophile antibodies are present in only 50% of patients<5 years and in about 80 to 90% of adolescents and adults with infectious mononucleosis. Importantly, the heterophile antibody test may be false-positive in some patients with acute HIV infection. The titer and prevalence of heterophile antibodies rise during the 2nd and 3rd week of illness. Thus, if the diagnosis is suspected and the heterophile antibody test is negative early in clinical illness (in the first week), testing can be repeated approximately 7 days later. Due to the potential for false positive or negative results, the Centers for Disease Control and Prevention (CDC) does not recommend heterophile antibodies to diagnose primary EBV infection (seeCDC: Laboratory Testing). However, a positive heterophile antibody test in the appropriate clinical situation is generally sufficient to confirm the diagnosis of primary EBV. Alternatively, EBV antibody testing can be performed. EBV-specific antibody testing is highly sensitive. The presence of IgM antibodies to the EBV viral capsid antigen (VCA) indicates primary EBV infection (these antibodies disappear within 3 months after infection). IgG VCA (EBV VCA-IgG) also develops early in primary EBV infection, but these antibodies persist for life. EBV nuclear antigen (EBNA-IgG) antibodies develop later (after 2 to 4 months ) in acute EBV infection and also persist for life. If EBV antibody titers are negative or indicate remote infection (ie, positive for IgG antibodies and negative for IgM antibodies), other diagnoses that can present with similar symptoms (eg, Human Immunodeficiency Virus (HIV) Infection , 