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Another Validation of Clinical Assessment and D-Dimer to Rule Out PE

Key point: Among patients with low or intermediate risk, the sensitivity and negative predictive value of D-dimer testing were 100%.

Citation: Gupta RT, Kakarla RK, Kirshenbaum KJ, et al. D-dimers and efficacy of clinical risk estimation algorithms: Sensitivity in evaluation of acute pulmonary embolism. AJR Am J Roentgenol. 2009; 193: 425-430.

Despite research showing that clinically important pulmonary embolism (PE) can be excluded when patients with low clinical probabilities have negative D-dimer test results, many clinicians continue to order pulmonary computed tomography angiographs (CTAs) in virtually every patient with suspected PE.

Researchers conducted this study at a community teaching hospital in Chicago to determine the accuracy of clinical risk assessment plus D-dimer testing in 627 emergency department patients in whom clinicians considered PE as a diagnostic possibility.

According to Geneva scores, the proportions of patients with low, intermediate and high probability of PE were 45%, 53%, and 3%, respectively. Outcomes were as follows:

  • Among 69 low-probability patients with negative D-dimer test results (<1.2 mg/L), CTA showed no PE cases.
  • Among 103 intermediate-probability patients with negative D-dimer test results, CTA showed no PE cases.
  • Among 212 low-probability patients with positive D-dimer test results, CTA showed six cases of PE.
  • Among 227 intermediate-probability patients with possible D-dimer test results, CTA showed 17 cases of PE.

Among patients with low or intermediate risk of PE, the sensitivity and negative predictive value of D-dimer testing were 100% (i.e., no false-negatives were reported).

For patients with high clinical probability, the current consensus is to skip D-dimer testing and go directly to imaging. Published in J Watch Gen Med, August 13, 2009 – Allan S. Brett, MD.

CDC Issues Guidance for School Districts for Upcoming Academic Year

Key point: Social disruption should be considered in decisions to dismiss students due to H1N1 flu.

Citation: Updated guidance for schools for the fall flu season. Centers for Disease Control and Prevention. 2009. Available at:

When contemplating school dismissals for flu, officials should balance the goal of reducing exposure to H1N1 virus against the social disruption associated with sending students home, the CDC recommend in new guidance issued for the upcoming academic year (grades K-12).

If H1N1 severity is the same as during the spring outbreak, the CDC advises that:

  • ill students and staff should remain at home for 24 hours after they are free of fever (without use of fever-lowering drugs);
  • those who are sick at school should be separated from others until they can be sent home.

If the virus shows increased severity compared with the spring outbreak:

  • students and staff should be screened on arrival at school and sent home if ill;
  • people at high risk for complications or with ill household members should stay home;
  • sick people should say home for at least 7 days, even if they become asymptomatic.

Obtaining Urine Specimens in Young Children: Bag vs. Catheter

Key point: Don’t rely on bag-obtained specimens alone.
Citation: Etoubleau C, Reveret M, Brouet D, et al. Moving from bag to catheter for urine collection in non-toilet-trained children suspected of having urinary tract infection: A paired comparison of urine cultures. J Pediatr. 2009; 154: 803-806.

Urine collection methods in young children who are not toilet trained are difficult and unreliable. In this prospective cohort study, researchers from two emergency departments in France collected urine specimens by bag and then by catheter in 192 children (age < 3 years; 72% girls) who had unexplained fever and positive urinalysis results from bag-obtained specimens.

Catheter-obtained specimens were positive (defined as ≥ 103 CFU/mL, one species only) in 53% of children, negative in 38%, and contaminated in 8%.

Corresponding results for bag-obtained specimens were 48% positive, 21% negative, and 30% contaminated. Compared with results from catheter-obtained specimens, bag-obtained specimen cultures had a false-positive rate of 7.5% and a false-negative rate of 29%.

[Published in J Watch General Med, July 7, 2009 – Howard Bauchner, MD.]

Travel and Venous Thromboembolism

Key point: Results of a meta-analysis showed a significant elevation in risk that increased with the duration of the journey.

Citation: Chandra D, Parisini E, Mozaffarian. Travel and risk for venous thromboembolism. Ann Intern Med. 2009; 151(3): 180-190.

Concern about travel-related venous thromboembolism (VTE) has recently attracted public attention. To examine the risk for VTE in travelers, these investigators conducted a literature analysis of 14 studies (two cohort, 11 case-control, and one case-crossover) with a total of 4,055 cases of VTE. The mode of travel in the studies varied (five air-only, nine air or surface), and the outcomes evaluated were deep venous thrombosis alone in seven, pulmonary embolism (PE) or DVT in five, and PE alone in two.

Compared with non-travelers, the pooled relative risk for VTE in travelers across all studies was 2.0 (P<0.001). However, significant heterogeneity resulted from differences in study design – specifically, in the selection criteria for controls.

The pooled risk estimate was somewhat higher for air travel than for surface travel. When duration of travel was assessed, the risk for VTE rose at a statistically significant 18% per two-hour increase in travel duration.
[Published in J Watch Cardiol, August 12, 2009 – Joel M. Gore, MD.]

Abstracts in Urgent Care: October, 2009