[Predictive value of blood cell parameters in the diagnosis of vasovagal syncope in children]

Objective: To investigate the predictive value of blood cell parameters in children with vasovagal syncope (VVS). Methods: In this case-control study, the VVS group included 111 patients with unexplained syncope or prodromata who were diagnosed with VVS by head-up tilt test in the Second Xiangya Hospital, Central South University from January 2018 to October 2020, and 111 healthy children were enrolled as control. The differences in blood cell parameters between the 2 groups were compared by t test and Mann-Whitney U test. Multivariate binary Logistic regression was used to analyze the independent correlation factors of VVS, and receiver operating characteristic (ROC) curve to explore the predictive value of blood cell parameters for diagnosing VVS. Results: Sex composition ratios were consistent in the 2 groups (51 males vs. 60 females), while the age of the VVS group was higher than that of the control group (11.0 (8.0, 12.5) vs. 8.0 (7.0, 11.0) years, Z=4.39, P<0.001). Compared with the control group, VVS group had lower level of white blood cell (WBC) (6.0 (5.3, 7.1)×10⁹ vs. 8.6 (6.7, 10.1)×10⁹/L, Z=-7.96, P<0.001), lymphocyte (LY) (2.3 (1.9, 2.7)×10⁹ vs. 4.0 (2.8, 6.3)×10⁹/L, Z=-8.49, P<0.001), lymphocyte ratio (0.39 (0.33, 0.44) vs. 0.52 (0.37, 0.69), Z=-5.59, P<0.001), monocyte (0.3 (0.3, 0.4)×10⁹ vs. 0.4 (0.3, 0.6)×10⁹/L, Z=-6.19, P<0.001), eosinophil (0.1 (0.1, 0.2)×10⁹ vs. 0.2 (0.2, 0.4)×10⁹/L, Z=-5.75, P<0.001), mean corpuscular-hemoglobin concentration (MCHC) ((328±12) vs. (333±11) g/L, t=-3.27, P<0.001) and blood platelet (263 (235, 313)×10⁹ vs. 341 (295, 409)×10⁹/L, Z=-2.69, P<0.001), but higher neutrophil ratio (0.53 (0.48, 0.58) vs. 0.37 (0.22, 0.54), Z=5.86, P<0.001), hematocrit (0.39±0.04 vs. 0.37±0.04, t=2.75, P=0.006), mean corpuscular volume (MCV) (85 (82, 88) vs. 81 (78, 84) fl, Z=5.56, P<0.001), mean corpuscular hemoglobin (28 (27, 29) vs. 27 (26, 28) pg, Z=3.39, P=0.001), red cell distribution width (39 (37, 41) vs. 37 (36, 40) fl, Z=4.02, P<0.001) and mean platelet volume (11 (10, 11) vs. 10 (9, 11) fl, Z=2.81, P=0.005) levels. After adjusting for confounding factors such as sex and age, LY (OR=0.42, 95%CI 0.29-0.62, P<0.001), WBC (OR=0.75, 95%CI 0.59-0.95, P=0.015), MCHC (OR=0.94, 95%CI 0.91-0.97, P<0.001) were independent negative correlation factors of VVS, while MCV (OR=1.08, 95%CI 1.01-1.15, P=0.021) was independent positive correlation factor. ROC curve showed that the combination of LY, WBC, MCV and MCHC had acceptable predictive value for the diagnosis of VVS, with area under curve of 0.88, sensitivity of 0.80, specificity of 0.83, and Youden index of 0.63. Conclusions: Compared with healthy children, the blood cell parameters usually change in those with VVS. Combination of LY, WBC, MCHC and MCV can facilitate the diagnosis of VVS in children with unexplained syncope or prodromata.