Can we defer/omit a type and screen blood test for pregnant women who know their blood type?

BACKGROUND

Current clinical practice in many emergency departments (EDs) includes checking a type and screen blood test (T&S) for Rhesus (Rh) status on all pregnant patients presenting with vaginal bleeding or abdominal pain. The test is expensive, and awaiting results may delay disposition.

OBJECTIVE

To determine if there is a subset of pregnant women who reliably know their blood type and for whom a T&S blood test to determine Rh status can be safely omitted or deferred.

METHODS

A prospective study at two associated urban academic centers with an annual ED census of 150,000 patients was performed between January 2007 and June 2008. Pregnant patients who had a T&S obtained as part of their ED evaluation were enrolled. Subjects completed a standardized data form that requested demographic information and were asked to select "no," "maybe," or "yes, definitely" if they knew their blood type. Standard descriptive statistics with 95% confidence intervals were performed.

RESULTS

There were 319 pregnant women enrolled in the study. Among the 106 subjects that reported "yes, definitely" they knew their blood type, 103 (97.2%; 95% confidence interval [CI] 94.0-100%]) identified their correct blood type and 105 (99.1%; 95% CI 97.2-100%) identified their correct Rh status. None of these subjects selected a positive Rh when they were in fact a negative Rh. All 14 (13.2%) subjects with a negative Rh status identified themselves as having a negative Rh.

CONCLUSION

Pregnant women reporting that "yes, definitely" they know their blood type, are reliable. Deferring T&S testing test may be reasonable.