Appendicitis Clinical Decision Rules
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
- 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).
- 1 point for –
- 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.