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Pretest Probability for PE: Structured Scoring System or Clinical Judgment?

Summary and Comment |
March 22, 2013

Pretest Probability for PE: Structured Scoring System or Clinical Judgment?

  1. Daniel J. Pallin, MD, MPH

Your gut feeling is probably as accurate as a structured score like the Wells score for pulmonary embolism.

  1. Daniel J. Pallin, MD, MPH

Quantitative estimates of the likelihood of pulmonary embolus (PE) are commonly used in research protocols and have infiltrated routine practice in many settings. But are these structured scores better than a physician's judgment? Investigators reviewed data for 1038 French and Belgian patients who had been included in a prospective cohort study of suspected PE.

In the original prospective study, emergency physicians (including physicians in training) had recorded their gestalt impression of the likelihood of PE (low, moderate, or high) as well as clinical variables. In the current study, researchers retrospectively calculated the Wells score and the revised Geneva score, and compared them to the physicians' gestalt.

Clinical judgment outperformed the structured scores. For patients categorized as low probability, the prevalence of PE was 8% when the assessment was by clinical gestalt versus 13% when the assessment was by the revised Geneva or Wells scores. For patients categorized as high probability, the prevalence of PE was 72% when the assessment was by gestalt, 69% by the revised Geneva score, and 58% by the Wells score.

Comment

Scoring systems are appealing, because they are objective, transferable from one setting to the next, and take the form of numbers, which facilitates research. On the other hand, they take time to calculate, are distracting, and their scientific flavor can cause us to overestimate their value. This study corroborates prior research (JW Emerg Med Sep 27 2005) in showing that gestalt is the best way to assess the likelihood of PE before testing. Evidence-based medicine teaches us that sophisticated laboratory science cannot predict clinical outcomes, and we are learning the same lesson about the complex tools of the clinical research “lab.” Structured assessments derived from clinical trials should displace the physician's judgment only when there is evidence of benefit.

Citation(s):

Reader Comments (1)

ROBERT BADGETT Physician, Internal Medicine, KUSM-W

I share the commenter's frustration with using prediction rules during busy clinical practice. However, I believe this commentary is overly positive on gestalt in this observational study. First, the study has problems with the internal validity of its conclusion. Physicians were queried the components of the Wells and Geneva rules when they were asked their gestalt prediction. Did the availability of these questions affect the physicians as they formulated their gestalt? Having the prediction rules available in the emergency room has been associated improve physician decision making.(1) Also, gestalt prediction was not provided by the physicians in 28% of cases. Were these the trickiest cases in which gestalt would suffer the most? Lastly, the study did not stratify the accuracy of gestalt by experience of the examiner.

Second, randomized controlled trials show that physicians pursue imaging in spite of low pre-test probability of pulmonary embolism; a third of imaging for embolism may not be necessary(20) and avoidance of imaging in low probability patients is a goal of http://www.choosingwisely.org. Although not studied in the setting of pulmonary embolism, in other clinical settings, prediction rules that are well embedded in work flow and part of treatment pathway, improve decision making - especially for low risk patients.(3-4) The better integrated the work flow, the better the effect.(4)

Lastly, I agree that prediction rules by themselves, not embedded into workflow and not part of a treatment pathway, have unclear value.(5)

References:
1. Roy PM, Meyer G, Vielle B, Le Gall C, Verschuren F, Carpentier F, Leveau P, Furber A; EMDEPU Study Group. Appropriateness of diagnostic management and outcomes of suspected pulmonary embolism. Ann Intern Med. 2006;144(3):157-64. PMID: 16461959.
2. Venkatesh AK, Kline JA, Courtney DM, Camargo CA, Plewa MC, Nordenholz KE, Moore CL, Richman PB, Smithline HA, Beam DM, Kabrhel C. Evaluation of pulmonary embolism in the emergency department and consistency with a national quality measure: quantifying the opportunity for improvement. Arch Intern Med. 2012;172(13):1028-32. doi: 10.1001/archinternmed.2012.1804. PMID: 22664742; PMCID: PMC3775003.
3. McGinn TG, McCullagh L, Kannry J, Knaus M, Sofianou A, Wisnivesky JP, Mann DM. Efficacy of an evidence-based clinical decision support in primary care practices: a randomized clinical trial. JAMA Intern Med. 2013;173(17):1584-91. doi: 10.1001/jamainternmed.2013.8980. PMID: 23896675.
4. Yealy DM, Auble TE, Stone RA, Lave JR, Meehan TP, Graff LG, Fine JM, Obrosky DS, Mor MK, Whittle J, Fine MJ. Effect of increasing the intensity of implementing pneumonia guidelines: a randomized, controlled trial. Ann Intern
Med. 2005;143(12):881-94. PMID: 16365469.
5. Poses RM, Cebul RD, Wigton RS. You can lead a horse to water--improving physicians' knowledge of probabilities may not affect their decisions. Med Decis Making. 1995;15(1):65-75. Erratum in: Med Decis Making 1995;15(2):179. PMID: 7898300.

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