Abstract: BACKGROUND: Clinically, the proportion of atypical lymphocytes is often used as an auxiliary diagnostic indicator for infectious mononucleosis, but the combined application of basophils and the proportion of atypical lymphocytes is rarely reported.
OBJECTIVE: To investigate the correlation of peripheral blood basophil and atypical lymphocyte proportions with disease severity and immune activation in patients with infectious mononucleosis, and to evaluate their auxiliary diagnostic value.
METHODS: Forty-five patients with infectious mononucleosis were enrolled as the study group and divided into severe group (n=14) and mild-to-moderate group (n=31) according to disease severity. Additionally, 30 age- and sex-matched healthy individuals undergoing physical examination were selected as the control group. Fasting peripheral venous blood was collected and stained with Wright-Giemsa compound stain. Morphological changes of lymphocytes were observed under a microscope, and the proportion of atypical lymphocytes was calculated. White blood cell count, basophil count, and basophil percentage were measured using an automatic hematology analyzer. Pearson correlation analysis was used to assess the correlation between basophil and atypical lymphocyte proportions. Receiver operating characteristic curve analysis was performed to evaluate the diagnostic value of basophil and atypical lymphocyte proportions for infectious mononucleosis.
RESULTS AND CONCLUSION: Basophil count, basophil percentage, and atypical lymphocyte proportion were significantly higher in the study group than in the control group (P < 0.05). These parameters were also significantly higher in the severe group than in the mild-to-moderate group (P < 0.05). Pearson correlation analysis showed that the proportion of atypical lymphocytes was positively correlated with basophil count and basophil percentage in patients with infectious mononucleosis (P < 0.05). Receiver operating characteristic curve analysis revealed that the area under the curve for basophil count, basophil percentage, and atypical lymphocyte proportion was 0.816, 0.726, and 0.857, respectively, and the combined area under the curve for these indicators was 0.952. These findings indicate that basophil and atypical lymphocyte proportions have high diagnostic values for infectious mononucleosis and can serve as comprehensive reference indexes for assessing the intensity of immune response and disease severity in patients with infectious mononucleosis.

Key words: infectious mononucleosis, atypical lymphocytes, basophils, diagnostic value