A Case of Erythrocyte Condensation Caused by Mycoplasma Pneumoniae Infection.

Background: Blood routine testing was the most commonly used laboratory method in clinical practice. The results are often influenced by factors such as instruments, reagents, and samples, among which, the interference of cold agglutinin is a very rare element. In our article, we reported a case of red blood cell agglutination caused by Mycoplasma pneumoniae infection.

Methods: The number of blood cells were detected by blood routine analyzer with or without treatment at 37℃ water bath. The red blood cell agglutination was observed through blood smear staining. The cold agglutination test were performed using O-type red blood cells added into patient's plasma and refrigerated overnight at 4℃. We also used luminescent immunoassay technology to detect the content of MP antibodies in patient's serum.

Results: The patient's results were RBC (2.69 x 1012/L), MCH (48.5 pg), MCHC (522 g/L). Through a microscope, we observed red blood cell agglutination. The concentration of MP-igM was 60.37 AU/mL. The cold agglutination test was positive. Following a 37℃ water bath, the patient's results changed: RBC (3.85 x 1012/L), MCH (31.2 pg), MCHC (352 g/L). The phenomenon of massive agglutination of red blood cells has also disappeared.

Conclusions: The cold agglutinin produced by MP infection can alter the results of red blood cell. During the epidemic period of MP infection, it is important to pay attention to the phenomenon of abnormal elevation of MCHC in clinical practice.