LAUSR

Lactate dehydrogenase (LDH) levels in measles virus (MeV) reinfection cases for the diagnosis of measles have not been extensively studied. Thus, we evaluated the significance of serum LDH in the immune response of patients with MeV reinfection in comparison with those of patients with primary infection. Among 70 patients who tested positive for MeV‐RNA, 42 with high MeV–specific IgG avidity (HA) were suspected as cases of reinfection and 28 with low MeV–specific IgG (LA) were suspected as cases of primary infection. The viral loads in the HA group were also lower than those in the LA group (P < 0.001). The titers of MeV‐specific IgM and IgG in the HA group were significantly lower and higher, respectively, than those in the LA group (P < 0.001). The total LDH and LDH isozyme levels were elevated in the LA group compared with those in the HA group (P < 0.001). Through receiver operating characteristic curve analyses, we determined that the area under the curve of total LDH level was 0.87 (95% CI 0.74–1.00) and that the discriminatory accuracy was high for total LDH and all isozymes. By stepwise binary logistic regression analysis considering MeV‐specific IgG avidity, we developed a model using IgG, IgM, and total LDH as explanatory variables, which was optimal for distinguishing the LA and HA groups (adjusted R2 = 0.773, P < 0.001). Thus, the serum LDH level in addition to IgM and IgG may be useful parameters for differentiating MeV reinfection from primary infection.