White blood cell count as a predictor of the severity of sickle cell disease during pregnancy

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Abstract

Objective

Increasing epidemiological evidence implicates leukocytosis as a major risk factor for poor outcome in non-pregnant sickle cell disease (SCD) patients. The aim of this study was to investigate whether steady-state white blood cell (WBC) count can predict SCD-related problems in pregnancy.

Design

Retrospective observational study of 40 SCD pregnant women who had their antenatal care at Guy's & St Thomas’ NHS Trust, London. Twenty-six women developed clinical complications related to SCD during their pregnancy (painful crisis, chest symptoms, infections, severe anaemia requiring blood transfusion, pre-eclampsia, and/or thromboembolism) and 14 remained asymptomatic. The steady-state leukocyte counts early in pregnancy were compared between the two groups and receiver operator characteristics (ROC) curve was plotted for different values of WBC.

Results

Compared to asymptomatic patients, women who developed SCD-related complications had significantly higher total WBC count [11.2 × 109 L−1 (SD 3.22) versus 8 × 109 L−1 (2.8), p < 0.01], higher lymphocyte count [3 × 109 L−1 (1.62) versus 1.6 × 109 L−1 (0.65), p < 0.01] and higher monocyte count [0.8 × 109 L−1 (0.47) versus 0.4 × 109 L−1 (0.21), p < 0.01]. The neutrophil count showed a similar trend but the difference did not reach statistical significance [6.6 × 109 L−1 (2.29) versus 5.7 × 109 L−1 (2.15), p = 0.22]. The area under the ROC curve was 74% (95% CI: 56–92).

Conclusion

WBC count early in pregnancy was significantly higher in women who subsequently developed clinical problems related to SCD. The WBC may be used as a predictor of the severity of SCD in pregnancy.

Introduction

Most women with sickle cell disease (SCD) now survive to reproduce, with an average life expectancy of approximately 50 years in the developed world [1]. Sickle cell crises occur more frequently during pregnancy [2]. The morbidity and mortality of the condition is high in pregnancy [3] and affected women are more at risk of stillbirth, pre-eclampsia, preterm delivery and poor fetal growth [4], [5]. There are considerable differences in the type and severity of clinical manifestations among pregnant women and their babies.

Research on SCD has recently focused on the role of leukocytes [6], [7], [8]. Increasing epidemiological evidence implicates leukocytosis at steady-state (i.e. when not in crisis and with no detectable infection) as a major risk factor for poor outcome in non-pregnant SCD patients. SCD has been associated with high steady-state leukocyte count [9]. High steady-state neutrophil count has been correlated with clinical severity of SCD [10]. The previous studies excluded pregnant patients. Since high steady-state leukocyte counts predispose to greater severity of SCD in non-pregnant patients, we hypothesized that the same could be true during pregnancy.

The aim of this study was to investigate whether the early steady-state WBC count is associated with the clinical severity of SCD later in pregnancy.

Section snippets

Materials and methods

The study was carried out retrospectively at the maternity unit of Guy's and St Thomas’ NHS Foundation Trust, a London teaching hospital with 5800 deliveries per year and a multi-ethnic population with high risk for SCD. Women with SCD are enrolled into antenatal care as early as possible, are closely monitored by a multidisciplinary team consisting of obstetricians, haematologists and specialist midwives, with access to consultant obstetric physician. There is low threshold for admission in

Results

Forty-one women fulfilled the inclusion criteria; one was excluded for developing obstetric cholostasis (n = 40). The mean age was 29.9 years (range 19–40). Twenty-three patients had HbSS genotype and 17 had HbSC. The mean gestational age at the time of entry into antenatal care was 14.3 weeks (median 13, range 6–20). All pregnancies were singleton and all women were on oral folic acid 5 mg once daily. Eighteen women were on long-term prophylactic oral penicillin V 250 mg once daily and remained on

Comment

The classical view of SCD has always focused on the primary genetic defect: the abnormal sickle haemoglobin that polymerises when deoxygenated. Polymerisation within the red cell causes it to deform, become rigid, obstruct the blood flow, and produce acute and chronic tissue damage because of poor perfusion [7]. More recent studies see the sickle red cell in a wider context, as it interacts with the vascular endothelium and its surrounding cells [12] with mediation by different adhesion

References (17)

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