White Blood Cell Count as a Predictor of the Severity of Sickle Cell Disease During Pregnancy

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There is increasing epidemiological evidence that leukocytosis in the absence of infection is a major risk factor for a poor outcome in nonpregnant patients with sickle cell disease (SCD). Because most affected women now live long enough to reproduce, the present retrospective observational study was planned in 40 women with SCD and singleton pregnancies, 26 of whom had SCD-related complications while pregnant. These included painful crises, chest symptoms, infections, anemia requiring blood transfusion, preeclampsia, and thromboembolism. Steady-state white blood cell (WBC) counts were compared in women with and those without SCD-related complications early in the course of pregnancy. All the women were taking folic acid and nearly half of them were also taking 250 mg of oral penicillin V daily on a prophylactic basis. No difference was found in mean hemoglobin concentrations between women with and those without SCD-related complications. Those with complications did, however, have significantly higher mean total WBC counts early in pregnancy than did those who remained asymptomatic. Mean lymphocyte and monocyte counts also were significantly higher. Complications were associated with higher neutrophil counts as well, but not to a significant degree. Linear regression analysis failed to demonstrate a significant correlation between the number of SCD complications during pregnancy and WBC counts. The area under the receiver operating characteristic curve, reflecting the likelihood that total WBC counts early in pregnancy will correctly predict SCD complications, was 74%. If sensitivity is set to more than 90% to minimize false-negative results, the cutoff WBC count is 6.5 × 109/liter. This value is 92% specific and 43% specific, with positive and negative predictive values of 75%. The investigators conclude that the WBC count is a useful predictor of the severity of SCD in pregnant women.