Diagnostic classification of referral decisions for the Oudega rule and GPs' probability estimates.
| Oudega rulea | GP estimate (cutoff 10%)b | GP estimate (cut off 20%)b | |
|---|---|---|---|
| Total referrals, n % of al patients suspected of having DVT (95% CI) | 502 51 (48 to 54) | 788 79 (76 to 81) | 648 65 (62 to 68) |
| Ultrasound negative referrals, n % of total referrals (95% CI) | 373 74 (70 to 78) | 655 83 (80 to 86) | 519 80 (77 to 83) |
| Total non-referrals, n % of al patients suspected of having DVT (95% CI) | 500 49 (47 to 53) | 214 21 (19 to 24) | 354 35 (32 to 38) |
| DVT failures in non-referrals, nc % of total non-referrals (95% CI) | 7 1.4 (0.4 to 2.4) | 3 1.4 (0.0 to 3.0) | 7 2.0 (0.5 to 3.4) |
↵a The Oudega rule uses a threshold of 3 points: patients with a score ≤3 were not referred for imaging (see Table 1).
↵b In this scenario, patients with a GP probability estimate below 10% or 20% were considered not referred for imaging
↵c No fatal or near-fatal thrombo-embolic events occurred in any of these DVT failures in non referrals. DVT = deep venous thrombosis.