Reference values and predictors of white blood cell subset counts: a cross-sectional study among HIV seronegative pregnant women in Zimbabwe

Objective: To identify predictors and develop reference values of white blood cell subset counts for pregnant black women in Zimbabwe. Study design: In this cross-sectional study, multiple linear regression (MLR) analysis was employed to assess the relationship of WBC subset counts with age, gestational age, gravidity, season, serum retinol, β-carotene, ferritin, folate and α-1 antichymotrypsin among 998 women 22–35 weeks pregnant attending antenatal care (ANC) in Harare, Zimbabwe. Results: Mean age was 24.0 (95% CI; 23.6–24.4), range 14–45 years. The mean gestational age was 29.2 (95% CI; 29.0–29.4), range 22–35 weeks. Median gravidity was 2, range 1–9. Predictors of neutrophil counts were gestational age, season and serum ferritin, the latter in interaction with gravidity (interaction, p=0.016). Mean lymphocyte count was 0.13×10 9 cells/l higher in gravida >4 than gravida 1–3, and 0.35×10 9 cells/l higher in the late rainy than other seasons. Predictors of monocyte counts were gestational age, serum folate and season, while eosinophil counts declined with advancing gestation. Reference values adjusted or unadjusted for identified predictors were different from those of pregnant and non-pregnant white women reported in the literature. Conclusions: Gravidity, season and micronutrient status influence WBC counts during pregnancy and therefore are of physiological and clinical importance. WBC reference values in the literature were not applicable obviating the need for local reference values.