Table 6
| Author, date and country | Patient group | Study type (level of evidence) | Outcomes | Key results | Study weaknesses |
|---|---|---|---|---|---|
| NPV = Negative predictive value, NLR = Likelihood ratio for negative result. | |||||
| Wells PS et al, 1995, Canada | 214 consecutive patients referred for investigation of ?DVT. | Prospective cohort | Prevalence | 25% | No sample size calculation Excluded patients with inconclusive venograms or plethysmogram |
| Sensitivity | 88% (CI 77, 96) | ||||
| Specificity | 77% (CI 63, 80) | ||||
| NPV | 95% (CI 89, 98) | ||||
| NLR | 0.16 | ||||
| Brenner B et al, 1995, Israel | 86 consecutive patients referred for investigation of ?DVT | Prospective cohort | Prevalence | 58% | Small patient numbers. No sample size calculation. No confidence intervals |
| Sensitivity | 94% | ||||
| Specificity | 61% | ||||
| NPV | 88% | ||||
| NLR | 0.1 | ||||
| Turkstra F et al, 1996, Netherlands | 234 consecutive patients referred for ?DVT or ?PE | Prospective cohort | Prevalence | 27% | No sample size calculation (but good numbers) |
| Sensitivity | 100% (CI 95, 100) | ||||
| Specificity | 58% (CI 50, 65) | ||||
| NPV | 100% (CI 96, 100) | ||||
| Janssen MC et al, 1997, Netherlands | 132 patients referred to ED or OPD for investigation of ?DVT | Prospective cohort | Prevalence | 67% | No sample size calculation. Technique of assay may have affected results. Reference standard not applied to all patients |
| Sensitivity | 61% (CI 51, 71) | ||||
| Specificity | 90% (CI 81, 99) | ||||
| NPV | 52% (CI 29, 75) | ||||
| NLR | 0.43 | ||||
| Ginsberg FS et al, 1997, Canada | 398 consecutive patients referred to thromboembolic OPD as first episode of ?DVT | Prospective management study | NPV d-dimer alone | 97.1% (CI 94.5, 98.8) | No sample size calculation. Reference standard not applied to all patients |
| NPV d-dimer and plethysmography together | 98.5% (CI 96.3, 99.6) | ||||
| Mayer W et al, 1997, Austria | 108 consecutive patients referred to vascular laboratory as ?DVT | Prospective cohort | Prevalence | 31% | Small patient numbers. No sample size calculation. Used single ultrasound as reference standard |
| Sensitivity | 100% (CI 89, 100) | ||||
| Specificity | 75% (CI 63, 84) | ||||
| NPV | 100% (CI 94, 100) | ||||
| Wildberger JE et al, 1998, Germany | 250 consecutive patients referred for venography | Prospective cohort | Sensitivity | 96% | No sample size calculation. Patient selection bias. No confidence intervals |
| Specificity | 59% | ||||
| NPV | 97% | ||||
| NLR | 0.06 | ||||
| Wells PS et al, 1998, Canada | 496 consecutive outpatients referred with ?DVT | Prospective cohort | Overall sensitivity | 94% | No sample size calculation. Patient selection bias. No confidence intervals |
| Overall specificity | 71% | ||||
| NPV | 98% (CI 96, 99) | ||||
| NLR | 0.08 | ||||
| Low pretest probability | |||||
| Sensitivity | 87% | ||||
| Specificity | 76% | ||||
| NPV | 99% (CI 97, 100) | ||||
| NLR | 0.17 | ||||
| Medium pretest probability | |||||
| Sensitivity | 89% | ||||
| Specificity | 64% | ||||
| NPV | 97% (CI 90, 99) | ||||
| NLR | 0.17 | ||||
| High pretest probability | |||||
| Sensitivity | 98% | ||||
| Specificity | 54% | ||||
| NPV | 86% (CI 42, 97) | ||||
| NLR | 0.04 | ||||
| Mauron T et al, 1998, Switzerland | 45 consecutive outpatients referred with ?DVT. | Prospective cohort | Prevalence | 33% | Small patient numbers. No sample size calculation. Wide confidence intervals |
| Sensitivity | 53% (CI 28, 78) | ||||
| Specificity | 70% (CI 54, 86) | ||||
| NPV | 75% (CI 59, 91) | ||||
| NLR | 0.67 | ||||
| Carter CJ et al, 1999, Canada | 200 consecutive patients referred to diagnostic radiology department with ?DVT. Inpatients and outpatients | Prospective cohort | Prevalence | 28% | No sample size calculation. Used single ultrasound as reference standard. Wide confidence intervals |
| Sensitivity | 87% (CI 80, 96) | ||||
| Specificity | 79% | ||||
| NPV | 94% | ||||
| NLR | 0.16 | ||||
| Lennox AF et al, 1999, UK | 200 consecutive patients referred to diagnostic radiology department with ?DVT. Inpatients and outpatients | Prospective cohort | Prevalence | 23% | No sample size calculation. Incorrect test procedure likely to give falsely high sensitivities. No confidence intervals |
| Sensitivity | 91% | ||||
| Specificity | 82% | ||||
| NPV | 97% | ||||
| NLR | 0.11 | ||||
| Farrell S et al, 2000, USA | 173 consecutive patients referred to ED with ?DVT (48) or ?PE (125) | Prospective clinical trial | Prevalence | 33% | Did not recruit all patients required. Used single ultrasound as reference standard. Wide confidence intervals |
| Sensitivity | 56% (CI 32, 81) | ||||
| NPV | 77% (CI 62, 92) | ||||
| NLR | 0.61 (CI 0.34, 1.11) | ||||
| Van der Graaf F et al, 2000, Netherlands | 112 outpatients referred to department | Prospective cohort | Prevalence | 50% | Small patient numbers. No sample size calculation. Wide confidence intervals |
| Sensitivity | 80% (CI 66, 90) | ||||
| Specificity | 94% (CI 83, 99) | ||||
| NPV | 82% (CI 70, 91) | ||||
| Likelihood ratio for negative result (NLR) | 0.21 | ||||
