Objective: This study was done to compare the results of Paul-Bunnel and immunoblot tests, which are routinely used in our laboratory for the serological diagnosis of Epstein-Barr Virus (EBV) infection.

Material and Methods: Paul-Bunnel and immunoblot tests were simultaneously performed in 200 serum samples which were sent to the Microbiology Central Laboratory of Uludağ University Faculty of Medicine with the prediagnosis of the EBV infection.

Results: In six of the seven patient samples which were diagnosed as acute infection by immunoblot results, Paul Bunnel test was found to be positive at any titer (even lower titers) (p<0.05). However, only two of the immunoblot detected acute EBV serology was found to be positive with Paul-Bunnel at a titer of ≥1/56 (p>0.05). Paul-Bunnel was positive (≥1/56) in one out of five patients in 0-19 age group in whom acute infection serology was detected with immunoblot, whereas one out of two patients in ≥20 age group with positive immunoblot result for acute infection had positive Paul-Bunnel test.

Conclusion: Investigation of the specific EBV antibodies by other methods such as immunoblot is crucial since heterophile antibody tests can only demonstrate IgM antibodies, do not give any idea about the stage of the disease and may lead to false positive and negative results in certain patients and age groups. In conclusion, it was suggested that positive results at low titer (≤1/56) and negative results, especially in 0-19 age group, should be confirmed by more specific tests which investigate antibodies against different antigenic structures of the virus. Besides, heterophile antibody positivity due to other infectious and non-infectious causes should always be considered.