Dynamic changes and influencing factors of leukocyte and platelet count in preterm infants

Abstract

Objective To investigate the dynamic changes and influencing factors of peripheral blood white blood cells (WBC), differential counts (DCs) and platelet (PLT) count in preterm infants to understand the changing characteristics of these blood parameters in preterm infants of different postnatal age, gestational age, and birth weight. Methods Totally 2 849 preterm infants admitted to the Department of Neonatology of Northwest Women's and Children's Hospital from November 30, 2011 to November 30, 2014 were retrospectively analyzed except for those diagnosed with infectious diseases, hematological system diseases, or immunologic diseases. All of the subjects were divided into seven groups based on their postnatal age, three groups based on gestational age and three groups based on birth weight, or male and female groups, respectively. Peripheral blood samples were obtained for determination of WBC, DCs and PLT. Statistical analysis was performed with one-way analysis of variance, t-test and Spearman linear correlation analysis. Results WBC, neutrophil (Ne), lymphocyte (Ly), monocyte (Mo), eosinophil (Eo), basophil (Ba) and PLT counts were significantly different among the seven groups of preterm babies of different postnatal age (F=172.00, 364.90, 34.88, 14.22, 80.82, 168.10 and 86.64, respectively, all P 2- ≤5 [(10.62±4.68)×109/L], further gradual decrease thereafter, and then being stable in day >14-≤21 and >21-≤30 [(10.54±3.09)×109/L and (10.27±3.70)×109/L, respectively]. PLT counts showed no significant change within one day after birth and in day >1-≤2 [(240.56±63.54)×109/L and (240.85±71.47)×109/L, respectively], then began to increase in day >2-≤5 [(249.21±80.55)×109/L], peaked in day >7-≤14 [(339.11±121.84)×109/L], and decreased gently and became stable finally. The changing trends of Ne and Ly were cross and inverted in day > 5-≤7. WBC, Ne, Ly, Mo, Eo, Ba and PLT counts of the preterm infants were all correlated with the postnatal age shown by Spearman linear correlation analysis (r=-0.46, -0.60, 0.18, -0.07, 0.33, -0.47 and 0.29, respectively, all P<0.01). With the increase of gestational age, WBC, Ne, Mo, and PLT counts increased, but Ly and Eo counts decreased. And all of the above showed significant difference (F=81.00, 124.49, 13.34, 18.35, 5.35 and 4.11, respectively, all P<0.05). While, the WBC, Ne, Mo, Ba and PLT counts showed positive relationship with the increase of birth weight (F=122.12, 133.09, 39.38, 13.77 and 21.24, respectively, all P<0.05). WBC, Ne and PLT counts of female infants were higher than those of male babies (t=16.35, 16.72 and 13.19, respectively, all P<0.05). Conclusions The peripheral WBC, DCs and PLT counts of preterm infants change dynamically with postnatal age with the remarkable variations on day >2-≤5 after birth and stable after 14 days of age. WBC, DCs and PLT counts might all be influenced by gestational age, birth weight and gender to some extend. Key words: Leukocyte count; Platelet count; Infant, premature