Background: Previous studies have shown that the mean monocyte volume was significantly increased in postsurgical patients with bacterial infection. To further validate its potential clinical usefulness, we compare the monocyte volume index (MV-index), which is defined as ΔMMV × ΔMMV-SD, (where the changes in Mean Monocyte Volume (MMV) and its Standard Deviation (MMV-SD) before and after surgery called ΔMMV and ΔMMV-SD, respectively) with PCT in terms of diagnostic sensitivity and specificity for post-surgical bacterial infection.
Methods: Blood samples from 223 cardiac surgical patients without postsurgical infection, and 63 cardiac surgical patients complicated with postsurgical bacterial infection were studied.
Results: There are no statistically significant differences for WBC count and monocyte percentage prior to or after surgery between postsurgical non-infected and infected patients. However, the MV-index is significantly increased in postsurgical infected patients when compared with non-infected patients (P<0.05). Furthermore, the MV-index was correlated well with PCT on the second and third day after surgery. The receiver-operating characteristics analysis reveals the MV-index and PCT have the similar areas under curves (0.908, 0.910 on the second day and 0.955, 0.956 on the third day postsurgery, respectively).
Conclusion: MV-index shows comparable sensitivity and specificity to PCT for predicting postsurgical bacterial infection. It may be an effective postoperative infection indicator for clinical diagnosis.