CLINICAL DECISION RULES UBIQUITOUS TO THE EMERGENCY CARE SETTING ARE NOT EFFECTIVE IN RESOLVING THE BURDEN OF UNNECESSARY CT IMAGING IN WOMEN EVALUATED FOR PULMONARY EMBOLISM

Purpose: We compared the gender differences in diagnostic yield of CT of the pulmonary arteries (CTPA) and, the diagnostic accuracy and effect of 2 validated clinical decision rules (CDRs) for PE that are widely used in the emergency care setting. 

Method: We compared the Pulmonary Embolism Rule-Out Criteria (PERC) and Modified Well’s Rule (Well’s) in women and men in a prospective, multi-center cohort with symptoms suggestive of PE.  Clinical evaluation and diagnostic testing was at the treating physician’s discretion.  Notably, patient characteristics, including age and comorbidites, were similar in both genders and reflected the heterogeneous population characteristic to the emergency care setting.  The presence or absence of CDR criteria were identified by the treating physician, at the time of evaluation, prior to PE testing.  Diagnostic yield was defined as the proportion of CTPA studies demonstrating a PE. Diagnostic accuracy was defined by the 45-day incidence of Venous Thromboembolism (VTE, PE and/or deep venous thrombosis[DVT]; blinded, adjudicated outcome using explicit criteria) and expressed as likelihood ratios (LR+ and LR-). The effect of CDRs was defined as the rate of CTPA in CDR-negative (PERC negative, Well’s score <2) patients

Result: We followed a total of 8774 patients (66% women) evaluated for PE. The overall rate of CTPA imaging was higher in women, resulting in a lower diagnostic yield: 21% in men compared to 10% in women (p<0.01). The 90-day prevalence of VTE was higher in men (9% men vs. 5% women, p<0.01). The diagnostic accuracies of PERC and Well’s did not differ (see table). There was no gender difference in the rate of CTPA imaging in either the PERC-negative (3% male and 6% female, p=0.29) or Well’s-negative (9% male and 9% female, p=0.28) groups.

	Men	Women	p-value
PERC
LR+	1.3	1.3	0.96
LR-	0.17	0.25	0.92
Modified Well’s Rule
LR+	2.4	2.3	0.99
LR-	0.41	0.44	0.97

Conclusion: Despite the successful integration of CDRs in the emergency care setting, the diagnostic yield of CTPA in women remains about half that of men even though the diagnostic accuracy and effect of CDRs does not differ by gender.  Given that the risk of cancer following radiation exposure from CTPA in women is approximately double that of men, improved methods to specifically risk-stratify women evaluated for PE are needed.