Are Pretest Clinical Probability Algorithms Used Before Obtaining Multidetector Computed Tomographic Pulmonary Embolism Studies?

• Published in: Canadian Association of Radiologists journal 2011-05, Vol.62 (2), p.107-109
• Main Authors: Machnowska, Matylda, MD, Burbridge, Brent E., MD, FRCPC, Fladeland, Derek, MD, FRCPC
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Aged; Aged, 80 and over; Algorithms; Biomarkers - analysis; Cardiovascular disease; Child; Computed tomographic angiography; D-dimer; Female; Fibrin Fibrinogen Degradation Products - analysis; Humans; Male; Medical procedures; Middle Aged; Predictive Value of Tests; Pretest clinical algorithms; Probability; Pulmonary embolism; Pulmonary Embolism - blood; Pulmonary Embolism - diagnostic imaging; Radiology; Retrospective Studies; Studies; Tomography; Tomography, X-Ray Computed - statistics & numerical data
• ISSN: 0846-5371; 1488-2361
• DOI: 10.1016/j.carj.2010.03.002

Current recommendations mandate that patients undergo D-dimer testing if there is a low pretest clinical probability of PE (Wells ≤4). A MDCT study or ventilation-perfusion lung scan should be pursued if the D-dimer result is positive, whereas a negative D-dimer result in this patient population has been shown to safely exclude PE [2-5], Van Belle showed the 3 month incidence of PE in patients who had an unlikely Wells clinical probability score and negative D-dimer result to be 0.5% [5], Patients with a high pretest probability of PE (Wells >4) should receive an MDCT or VQ scan, regardless of their D-dimer score [2-4]. Because of poor specificity, D-dimer has been suggested as not being a cost-effective examination for inpatients more than 79 years old, those who sustained trauma, those who had recent surgery, or those with a stay of more than 3 days in the hospital [7-9]. Also, the D-dimer test may show falsenegative results in patients on anticoagulants [7], Therefore, a MDCT PE study without a D-dimer measurement was considered to be the appropriate course of action in these patients. Up to 50% of D-dimer tests are negative in the 19th week of pregnancy, current recommendations remain that D-dimer testing should be performed in pregnant patients [4-8]. Collagen vascular disease was not considered to be a contraindication to D-dimer testing. The final assessment of each patient who had a MDCT PE examination resulted in the analysis of the MDCT PE radiologist report, patient demographics, documented pretest probability scores, and D-dimer test results. Results were analysed by using a χ^sup 2^ test. The prevalence of PE in those with an unlikely pretest clinical score and a positive D-dimer at our institution, 15.3%, is comparable to results published by Van Belle et al [5], who found a PE prevalence of 23.2% in this population. The prevalence of PE in the clinically selected population of patients who had MDCT PE studies performed at our institution is quite high, 19%, in comparison with literature ranges of 2%- 5% [10,1 1]. The prevalence of PE in the non- D-dimer group was 24% in comparison with recent literature rates of 9% at other institutions [10]. Therefore, the clinicians at our institution are definitely applying pre-MDCT PE examinations clinical algorithms. The rate of a positive MDCT PE examination at our institution, rather than being too low, is actually quite high in comparison with the findings of other investigators.