Pulmonary Vascular Disease |

The Increasing Use of D-Dimer Testing in Suspected Pulmonary Embolism FREE TO VIEW

Guy Soo Hoo, MD; Bruce Barack, MD; Sondra Vazirani, MD; Zhaoping Li, MD; Carol Wu, MD
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VA Greater Los Angeles Healthcare System and David Geffen School of Medicine at UCLA, Los Angeles, CA

Chest. 2015;148(4_MeetingAbstracts):918A. doi:10.1378/chest.2281445
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SESSION TITLE: Evaluation and Management of Venous Thromboembolism

SESSION TYPE: Original Investigation Slide

PRESENTED ON: Monday, October 26, 2015 at 04:30 PM - 05:30 PM

PURPOSE: In patients with a low index of suspicion for pulmonary embolism (PE) based on a clinical decision rule (CDR) and low D-dimer, CT pulmonary angiogram (CTPA) is not recommended. Nevertheless, CTPAs are frequently ordered, and up to one third may not meet the above criteria. A CDR using a Wells score > 4 and highly sensitive D-dimer with a decision threshold of < 500 ng/ml for ordering CTPAs has been in use at our hospital since 2007. This experience was analyzed to characterize utilization patterns and to identify additional characteristics of patients with a low likelihood for PE.

METHODS: The above guidelines were incorporated in an order entry menu for CTPA. Data was abstracted using a standardized case report form. The study was approved by our institutional review board (IRB).

RESULTS: Over a seven year period, 989 CTPAs were performed in patients with a mean age of 64 + 13 years, with 166 (16.8%) positive for PE. D-dimer measurements were obtained in 897 (90.6%). Only four with a D-dimer < 500 ng/ml (< 0.5%) had a CTPA positive for PE, two with Wells > 4. In subjects with a D-dimer < 1000 ng/ml, 21 CTPAs were positive (2.1%). When analyzed by negative CTPAs, 73 studies (7.4%) had a D-dimer < 500 ng/ml, 23 with Wells < 4 and 50 with Wells > 4. Using a D-dimer of <750 ng/ml, 203 studies (20.5%), 84 with Wells < 4 and 129 with Wells >4 were negative CTPAs. With a D-dimer of <1000 ng/ml, 316 (32%), 127 {12.8%] with a Wells < 4 and 189 with a Wells > 4 were negative CTPAs. The negative predictive value of the Wells score <4 and D-dimer of <750 ng/ml was 0.965 and D-dimer <1000 ng/ml was 0.962.

CONCLUSIONS: The near universal (>90%) measurement of D-dimer values in patients with suspected PE further enhanced identification of patients with low likelihood of PE. This suggests that D-dimer values of <750 ng/ml and <1000 ng/ml can be used as thresholds for decision making. Combined with a Wells score < 4, these D-dimer thresholds could expand the number of subjects in which CTPA can be safely deferred, decreasing utilization rates and radiation exposure. A prospective, randomized trial is required for further validation of this strategy.

CLINICAL IMPLICATIONS: Incorporating routine measurement of the D-dimer in conjunction with a CDR, prior to obtaining a CTPA may permit identification of additional low risk patients that can safely have CTPA deferred as part of their evaluation. A conservative decrease of 12.8% and possibly greater reduction in CTPA utilization could be realized using this strategy.

DISCLOSURE: The following authors have nothing to disclose: Guy Soo Hoo, Bruce Barack, Sondra Vazirani, Zhaoping Li, Carol Wu

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