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Platelet count may predict abnormal bleeding time among pregnant women with hypertension and preeclampsia

[La numération plaquettaire peut permettre de prédire le temps de saignement chez des parturientes atteintes d'hypertension et de pré-éclampsie]

R.J. McDonagh, MSC MD FRCSC^*,, J.G. Ray, MD FRCPC^,, R.F. Burrows, MD FRCSC, E.A. Burrows, BA MBA and M.J. Vermeulen, BSCN MHSC^¶

^* From the Department of Obstetrics and Gynecology, St. Joseph's Hospital and McMaster University; the
Department of Clinical Epidemiology and Biostatistics, McMaster University; the
Division of Critical Care, McMaster University, Hamilton, Ontario, Canada; the
Department of Obstetrics and Gynecology, Monash University, Clayton, Victoria, Australia; and the
^¶ Prehospital Care Program, Sunnybrook and Women's College Health Sciences Center, Toronto, Ontario, Canada.

Address correspondence to: Dr. R.J. McDonagh, Department of Obstetrics and Gynecology, St. James's Hospital, 301 James Street South, 2nd Floor-Fontbonne Building, Hamilton, Ontario L8N 4A6, Canada. Phone: 905-522-4941, ext. 4258; Fax: 905-521-6089; E-mail: rorymcdonagh{at}hotmail.com

Background: Anesthesiologists often require laboratory data to estimate the bleeding risk among hypertensive pregnant women prior to administering regional anesthesia. Many rely on the bleeding time (BT) in making this determination. We examined whether the platelet count can adequately predict BT among a group of hypertensive parturients.

Methods: This retrospective subgroup analysis, taken from a cohort of 2051 hypertensive pregnant women, comprises 87 individuals who underwent both a BT and platelet count prior to delivery. We calculated the correlation between the platelet count and BT at three platelet cut-off points with respect to prolonged BT of eight minutes or more.

Results: There was a significant negative correlation between platelet count at delivery and BT [r= -0.45, 95% confidence interval (CI) -0.26 to -0.60; P <0.0001]. All three platelet cut-off points had a sensitivity of less than 66% with negative predictive values below 75% for an abnormal BT. A platelet count 75 x 10⁹/L was specific for the presence of an abnormal BT (specificity 97.8%, 95% CI 91.7–100.0), with a positive predictive value of 95.5% (95% CI 83.1–100.0) and a positive likelihood ratio of 24 (95% CI 3.3–168).

Conclusions: In a group of hypertensive parturients, the platelet count appears to be very specific for predicting a prolonged BT. The platelet count may aid the anesthesiologist in determining the risk of bleeding from regional anesthesia. Given the study's potential for bias future research is needed to validate these findings.