Correlated expression of D-dimer concentrations with thrombotic burden in acute pulmonary embolism

Elevated d-dimer cut-off values for computed tomography pulmonary angiography-d-dimer correlates with location of embolism

BACKGROUND

Acute pulmonary embolism (APE) is a potentially fatal condition, and making a timely diagnosis can be challenging. Computed tomography pulmonary angiography (CTPA) has become the modality of choice, and this contributes to the increasing load on emergency room CT scanners. Our purpose was to investigate whether an elevated d-dimer cut-off could reduce the demand for CTPA while maintaining a high sensitivity and negative predictive value (NPV).

METHODS

We retrospectively reviewed all patients referred for CTPA with suspicion of APE in 2012, and collected d-dimer values and CTPA results. We investigated the diagnostic performance of d-dimer using a 0.5 mg/L cut-off and an age adjusted cut-off. We also evaluated a new and elevated cut-off. Cases were categorized according to their CTPA result into: no embolism, peripheral embolism, lobar embolism and central embolism. Finally we investigated a possible correlation between d-dimer values and location of embolism.

RESULTS

We included 1,051 CTPAs, from which 216 (21%) showed pulmonary embolism. There were concomitant d-dimer analyses in 822 CTPA examinations. The current 0.5 mg/L cut-off achieved a sensitivity and NPV of 99%. The age-adjusted cut-off achieved a sensitivity and NPV of 98%, and our suggested cut-off of 0.9 mg/L achieved a sensitivity and NPV of 97%.

CONCLUSIONS

We conclude that the elevated d-dimer cut-off of 0.9 mg/L achieved a high sensitivity and NPV, while reducing the number of CTPA by 27%. The correlation between d-dimer values and location of embolisms supports the suggestion of an elevated d-dimer value.

Does a clinical decision rule using D-dimer level improve the yield of pulmonary CT angiography?

OBJECTIVE

The objective of our study was to evaluate the impact of incorporating a mandatory clinical decision rule and selective d-dimer use on the yield of pulmonary CT angiography (CTA).

MATERIALS AND METHODS

Guidelines incorporating a clinical decision rule (Wells score: range, 0-12.5) and a highly sensitive d-dimer assay as decision points were placed into a computerized order entry menu. From December 2006 through November 2008, 261 pulmonary CTA examinations of 238 men and 14 women (mean age ± SD, 65 ± 12 years; range, 31-92 years) were performed. Eight patients underwent more than one pulmonary CTA examination. Charts were reviewed. The results of pulmonary CTA, the clinical decision rule, and d-dimer level (if obtained) were analyzed with the Student t test, chi-square test, or other comparisons using statistical software (MedCalc, version 11.0).

RESULTS

Of the pulmonary CTA examinations, 16.5% (43/261) were positive for pulmonary embolism (PE) compared with 3.1% (6/196) during the previous 2 years. The mean clinical decision rule score and mean d-dimer level were 5.5 ± 2.4 (SD) and 4956 ± 2892 ng/mL, respectively, for those with PE compared with 4.5 ± 2.1 and 2398 ± 2100 ng/mL for those without PE (both, p < 0.01). The negative predictive value of a clinical decision rule score of 4 or less and d-dimer level of less than 1000 ng/mL was 1.0. A clinical decision rule of greater than 4 and a higher d-dimer level were better predictors for PE, especially a d-dimer level of greater than 3000 ng/mL (odds ratio = 6.69; 95% CI = 2.72-16.43).

CONCLUSION

Guidelines combining a clinical decision rule with d-dimer level significantly improved the utilization of pulmonary CTA and positive yield for PE.