Article: Sensitivity and Specificity of a Rapid Whole-Blood Assay for D-Dimer in the Diagnosis of Pulmonary Embolism
Authors: Ginsberg JS, Wells PS, Kearon C, et al
Publication: Ann Intern Med. 1998;129:1006-1011
Study: Prospective cohort of 1177 consecutive patients with suspected PE underwent whole-blood D-dimer assay compared with diagnostic strategy for diagnosis of PE
Inclusion Criteria: consecutive patients 18 years or older with clinically suspected PE
Exclusion Criteria: suspected upper extremity DVT; no symptoms within 48 hours of presentation; treatment with anticoagulants for greater than 72 hours; life expectancy < 3 months; contraindication to contrast dye; geographic inaccessibility
Step 1: Are the results valid?
Step 1a: Was there an independent, blind comparison to a reference standard?
Yes, but did not use pulmonary angiography as reference standard and instead used a diagnostic strategy in which all patients had a VQ scan and US. Patients at highest risk underwent venography and pulmonary angiography if venography was negative. All patients with negative test results were followed for 3 months.
Step 1b: Did patient sample include appropriate spectrum of patients?
Yes, all patients suspected of having PE were included regardless of low, moderate, or high pre-test probability.
Step 1c: Did results influence the decision to perform reference standard?
No
Step 1d: Were methods of performing the test described in sufficient detail?
Yes
Step 2: What are the results?
| D-dimer result | PE present | PE absent | LR (95% CI) |
| positive | 167 | 310 | 2.7 ( 2.3-3.0) |
| negative | 30 | 670 | 0.22 (0.16-0.31) |
| total | 197 | 980 |
| Patient Subgroup | PE present | PE present | PE absent | PE absent |
LR (95% CI) |
LR (95% CI) |
| + D-dimer | - D-dimer | + D-dimer | - D-dimer | + D-dimer | - D-dimer | |
| low pretest probability | 19 | 5 | 163 | 516 |
3.3 (2.6-4.2) |
0.27 (0.13-0.60) |
| moderate pretest probability | 81 | 20 | 136 | 145 |
1.7 (1.4-1.9) |
0.38 (0.26-0.58) |
| high pretest probability | 67 | 5 | 11 | 9 |
1.7 (1.1-2.5) |
0.15 (0.06-0.41) |
Step 3: Will the results help me in caring for my patients?
Limitations
1. used complex diagnostic strategy instead of pulmonary angiography as "gold standard"
2. valid for whole-blood D-dimer by simpliRED assay with results reported as normal or abnormal
Strength
1. included data on pre-test probability
Conclusion
In patients with suspected PE, a normal D-dimer is useful for excluding the diagnosis in those with a low pre-test probability. A normal D-dimer does not exclude PE in pateints with moderate to high pretest probability