The role of platelet counts in the assessment of inpatient women with preeclampsia.

OBJECTIVE: Platelet count has been proposed as a screening test for generalized coagulopathy in women with preeclampsia. We performed this study to determine the relationship between platelet counts and the risk of abnormal coagulation and adverse maternal outcomes in women with preeclampsia.

METHODS: We used data from women in the PIERS (Pre-eclampsia Integrated Estimate of RiSk) database. Abnormal coagulation was defined as either an international normalized ratio result greater than and/or a serum fibrinogen level less than the BC Women's Hospital laboratory's pregnancy-specific normal range. The relationship between platelet counts and adverse maternal outcomes was explored using a logistic regression analysis. The sensitivity, specificity, positive predictive value, and negative predictive value of platelet counts in identifying abnormal coagulation or adverse maternal outcomes were calculated.

RESULTS: Abnormal coagulation occurred in 105 of 1405 eligible women (7.5%). The odds of having abnormal coagulation were increased for women with platelet counts < 50 × 10(9)/L (OR 7.78; 95% CI 3.36 to 18.03) and between 50 and 99 × 10(9)/L (OR 2.69; 95% CI 1.44 to 5.01) compared with women who had platelet counts above 150 × 10(9)/L. Platelet counts < 100 × 10(9)/L were associated with significantly increased odds of adverse maternal outcomes, most specifically blood transfusion. A platelet count of < 100 × 10(9)/L had good specificity in identifying abnormal coagulation and adverse maternal outcomes (92% [95% CI 91% to 94%] and 92% [95% CI 91% to 94%], respectively), but poor sensitivity (22% [95% CI 15% to 31%] and 16% [95% CI 11% to 23%], respectively).

CONCLUSION: A platelet count < 100 × 10(9)/L is associated with an increased risk of abnormal coagulation and maternal adverse outcomes in women with preeclampsia. However, the platelet count should not be used in isolation to guide care because of its poor sensitivity. Whether or not a platelet count is normal should not be used to determine whether further coagulation tests are needed.