Browsing by Author "Hogg, Melanie M"

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    D-Dimer and Exhaled CO2/O2 to Detect Segmental Pulmonary Embolism in Moderate-Risk Patients
    (2010-09) Kline, Jeffrey A.; Hogg, Melanie M; Courtney, D Mark; Miller, Chadwick D; Jones, Alan E; Smithline, Howard A; Klekowski, Nicole; Lanier, Randy
    Rationale: Pulmonary embolism (PE) decreases the exhaled end-tidal ratio of carbon dioxide to oxygen (etCO2/O2). Objectives: To test if the etCO2/O2 can produce clinically important changes in the probability of segmental or larger PE on computerized tomography multidetector-row pulmonary angiography (MDCTPA) in a moderate-risk population with a positive D-dimer. Methods: Emergency department and hospitalized patients with one or more predefined symptoms or signs, one or more risk factors for PE, and 64-slice MDCTPA enrolled from four hospitals. D-dimer greater than 499 ng/ml was test(+), and D-dimer less than 500 ng/ml was test(−). The median etCO2/O2 less than 0.28 from seven or more breaths was test(+) and etCO2/O2 greater than 0.45 was test(−). MDCTPA images were read by two independent radiologists and the criterion standard was the interpretation of acute PE by either reader. PE size was then graded. Measurements and Main Results: We enrolled 495 patients, including 60 (12%) with segmental or larger, and 29 (6%) with subsegmental PE. A total of 367 (74%) patients were D-dimer(+), including all 60 with segmental or larger PE (posterior probability 16%). The combination of D-dimer(+) and etCO2/O2(+) increased the posterior probability of segmental or larger PE to 28% (95% confidence interval [CI] for difference of 12%, 3.0–22%). The combination of D-dimer(+) and etCO2/O2(−) was observed in 40 patients (8%; 95% CI, 6–11%), and none (0/40; 95% CI, 0–9%) had segmental or larger PE on MDCTPA. No strategy changed the prevalence of subsegmental PE. Conclusions: In moderate-risk patients with a positive D-dimer, the et etCO2/O2 less than 0.28 significantly increases the probability of segmental or larger PE and the etCO2/O2 greater than 0.45 predicts the absence of segmental or larger PE on MDCTPA.
  • Thumbnail Image
    Item
    D-dimer threshold increase with pretest probability unlikely for pulmonary embolism to decrease unnecessary computerized tomographic pulmonary angiography
    (2012-04) Kline, Jeffrey A.; Hogg, Melanie M; Courtney, D Mark; Miller, Chadwick D; Jones, Alan E; Smithline, Howard A
    Background:  Increasing the threshold to define a positive D-dimer could reduce unnecessary computed tomographic pulmonary angiography (CTPA) for a suspected pulmonary embolism (PE) but might increase rates of a missed PE and missed pneumonia, the most common non-thromboembolic diagnosis seen on CTPA. Objective:  Measure the effect of doubling the standard D-dimer threshold for ‘PE unlikely’ Revised Geneva (RGS) or Wells’ scores on the exclusion rate, frequency and size of a missed PE and missed pneumonia. Methods:  Patients evaluated for a suspected PE with 64-channel CTPA were prospectively enrolled from emergency departments (EDs) and inpatient units of four hospitals. Pretest probability data were collected in real time and the D-dimer was measured in a central laboratory. Criterion standard was CPTA interpretation by two independent radiologists combined with clinical outcome at 30 days. Results:  Of 678 patients enrolled, 126 (19%) were PE+ and 93 (14%) had pneumonia. Use of either Wells’ ≤ 4 or RGS ≤ 6 produced similar results. For example, with RGS ≤ 6 and standard threshold (< 500 ng mL−1), D-dimer was negative in 110/678 (16%), and 4/110 were PE+ (posterior probability 3.8%) and 9/110 (8.2%) had pneumonia. With RGS ≤ 6 and a threshold < 1000 ng mL−1, D-dimer was negative in 208/678 (31%) and 11/208 (5.3%) were PE+, but 10/11 missed PEs were subsegmental and none had concomitant DVT. Pneumonia was found in 12/208 (5.4%) with RGS ≤ 6 and D-dimer < 1000 ng mL−1. Conclusions:  Doubling the threshold for a positive D-dimer with a PE unlikely pretest probability could reduce CTPA scanning with a slightly increased risk of missed isolated subsegmental PE, and no increase in rate of missed pneumonia.