Appendicitis Clinical Decision Rules

Featured on the LITFL Review #171 – Thanks to Dr. Anand “Swami” Swaminathan (@EMSwami) and the LITFL Review group for the shout out!

Originally published at Pediatric EM Morsels on October 17, 2014. Reposted with permission.

Follow Dr. Sean M. Fox on twitter @PedEMMorsels

Often the Ped EM Morsels discuss diagnoses that emphasize astute clinical skills and vigilance while minimizing the importance of laboratory testing.  Appendicitis is a great example of this!

Many of you already know my disdain for the ubiquitous WBC count (otherwise known as the “Last Bastion of the Intellectually Destitute” – Amal Mattu) and are also aware of the many Myths that are associated with Appendicitis.  This month’s Annals of Emergency Medicine (2014, Oct; 64(4)) addresses another often encountered issue with Appendicitis: the Clinical Decision Rules.

Clinical Decision Rules

  • The practice of medicine is becoming more complicated everyday.
  • Ideally, we would like to ensure that all patients get superior care regardless of where they receive their care.
  • Clinical Decision Rules are aimed at helping providers deliver consistent and high quality care.
  • Clinical Decision Rules integrate various features (history, exam, simple labs, etc) in an effort to predict the likelihood of a specific disease/condition.
  • Useful Clinical Decision Rules would stratify patients into Low, Moderate, and High Risk Groups.
    • Low Risk – Condition ruled-out. No testing.
    • Moderate Risk – “Test Threshold” – Requires further testing.
    • High Risk – “Treatment Threshold” – Condition ruled-in. No Testing… just treat!

Appendicitis and Clinical Decision Rules

  • There are two widely used Clinical Decision Rules for Appendicitis.
    • Alvarado Score
    • Pediatric Appendicitis Score
  • The Alvarado Score has been found to have better test characteristics than the Pediatric Appendicitis Score (although they vary only slightly).
  • The Alvarado Score is a 10-point Score:
    • 1 point for –
      • Migration of Pain
      • Anorexia
      • Nausea or vomiting
      • Rebound Pain
      • Elevated Temperature (greater than or equal to 99.2 F)
      • Left Shift (greater than or equal to 75% PMNs)
    • 2 points for – 
      • Right Lower Quadrant Tenderness
      • Leukocytosis (greater than or equal to 10,000/microL).
  • The Pediatric Appendicitis Score gives only 1 point for leukocytosis and gives no points for rebound pain while adding 2 points for RLQ pain with coughing, jumping, percussion.
  • Unfortunately, often theses clinical findings are not reliably reproduced (we all know if the ask a patient a question 3 times you’ll get at least 2 different replies – “Did you vomit?” “No.” “Did you vomit?” “No.” “Did you vomit?” “Oh, you mean throw up? Yes I did.”).

Pretest Probability Matters

  • The Ebell and Shinholser paper nicely demonstrates the fact that the performance of the Clinical Decision Rule for appendicitis is dependent upon the pretest probability.
    • At a pretest probability of 33%, even an Alvarado Score of 9 or 10 does not cross the Treatment Threshold.
    • At a pretest probability of 66%, even an Alvarado Score of <4 does not define a useful Low Risk group.
  • What determines the clinician’s Pretest Probability??
    • While clinical experience and illness scripts certainly play a role in the estimation of the Pretest Probability,…
    • I would also suggest that the Clinical Variables scored in the Clinical Decision score play a significant role in the determination of a Pretest Probability.
    • So if a patient has migratory pain, nausea/vomiting, fevers, RLQ tenderness and rebound, both the Pretest Probability and the Alvarado Score will be high.
    • Experienced clinicians will often perform as well as Clinical Decision Rules.
  • Stratification is not precise.
    • Determining a Pretest Probability is dependent upon many variables.
    • Deciphering it all into a nice number like “33%” or “50%” or “66%” is difficult.
    • Often we default to a general gestalt.
    • This underscores that fact that our job is as much art as it is science.

Moral of the Morsel

  • The diagnosis of appendicitis is a difficult one.
  • The WBC count still is the Last Bastion of the Intellectually Destitute!
  • Clinical Decision Rules can help when incorporated into a Clinical Pathway that help to standardize care across a regional population.
  • Nothing is better than your clinical experience and acumen.


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