Heterophile antibody (monospot) test vs EBV IgM Assay
CBC
Lymphocytosis (≥50% lymphocytes)
10% or more atypical lymphocytes
Hypersegmented neutrophils
Thrombocytopenia
LFTs
Elevations in AST and ALT is expected up to 5x
Suspected<unk>  during pregnancy (also need to rule out other pathology):
Epstein-Barr virus, cytomegalovirus, and HIV
Lymphocytosis (≥50% lymphocytes)
10% or more atypical lymphocytes
Hypersegmented neutrophils
Thrombocytopenia
10% or more atypical lymphocytes
Hypersegmented neutrophils
Elevations in AST and ALT is expected up to 5x
Epstein-Barr virus, cytomegalovirus, and HIV
Heterophile antibody (monospot) test
Up to 25% of patients in 1st week of symptoms may have false negative test
10% of adult patients with EBV infection will be persistently negative
Up to 50% of pediatric patients will be persistently negative
EBV IgM Assay
Carries 97% sensitivity and 94% specificity at symptom onset
Up to 25% of patients in 1st week of symptoms may have false negative test
10% of adult patients with EBV infection will be persistently negative
Up to 50% of pediatric patients will be persistently negative
Carries 97% sensitivity and 94% specificity at symptom onset
Infectious mononucleosis
Streptococcal pharyngitis 
Typhoid fever
Neisseria gonorrhoeae
AIDS fever of unknown origin
Diphtheria 
Ebola virus disease
Bacterial Tracheitis