A Review of Inappropriate D-Dimer Ordering at a Canadian Tertiary Care Centre
Bibliographic record
Abstract
Introduction The D-dimer has been validated for use in the diagnosis of venous thromboembolism (VTE). The high sensitivity of the assay allows for safe exclusion of VTE in patients with low pre-test probability. Pre-test probability scores such as the Wells score for Deep Vein Thrombosis (DVT) and Pulmonary Embolism (PE) have been established to help guide physicians on when to order a D-dimer in patients with suspected VTE. We sought to explore the landscape of D-dimer ordering at our institution and what clinical circumstances trigger D-dimer ordering. Methods We conducted a retrospective chart review of 237 patients in whom a D-dimer has been ordered over a 3-month period from January to March 2018 at the University of Alberta Hospital, Edmonton, Canada. Charts were reviewed for the following parameters: Specialty of ordering physician, apparent indication for ordering, patient risk factors for VTE and evidence of pre-test probability calculation. If no pre-test probability was recorded, we retrospectively calculated Wells DVT or PE scores depending on the apparent indication. We then reviewed subsequent investigations thought to be influenced by interpretation of the D-dimer. These included ventilation/perfusion scans (V/Q scan), ultrasound Doppler studies and Computerized Tomography pulmonary angiography (CTPA). Results Of the 237 charts reviewed, 84.4% of D-dimers were ordered in the Emergency Department while only 14.3% were drawn on admitted patients. Sixty-nine percent of the patients were identified as having at least one risk factor for the development of VTE with prolonged hospitalization (5.5%) and personal history of VTE (4.2%) being the most common. Indication for ordering was suspected VTE in 76.3% of patients while the indications was unclear in 12.7% of patients. An initial pre-test probability score was recorded for only 3 patients. Of the D-dimers ordered, 47.7% were above the upper limit of normal (≥ 0.50 mg/L) and considered a positive test. Forty five CTPAs and 27 V/Q scans were performed with only 4 (1.69%) and 6 (2.53%) confirming the presence of pulmonary emboli, respectively. Doppler ultrasounds were performed on 18 patients (7.6%) with only one confirming a DVT. Conclusions Our data shows that the majority of physicians at our institution fail to utilize pre-test probability tools prior to ordering a D-dimer. This leads to unnecessary costs, overuse of imaging studies and results in low rates of positive scans. Disclosures Wu: Bayer: Other: Local PI for trial ; BMS-Pfizer: Other: Local PI for trial ; Daiichi-Sankyo: Other: Local PI for trial .
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.012 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.006 | 0.009 |
| Science and technology studies | 0.002 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".