Playing by the Rules: Using Decision Rules Wisely Part 2, Nontraumatic Conditions

Since the original Alvarado study was published, multiple small studies have attempted to validate or otherwise retrospectively assess the utility of this rule. A frequently cited systematic review of 42 prospective and retrospective studies by Ohle et al found that a score of <5 showed a sensitivity of 99% overall (96% in men, 99% in women, and 99% in children) for ruling out admission/observation of patient with suspected appendicitis, though the specificity for ruling in the diagnosis at scores 7 and higher was only 81% overall.¹⁰

However, a more recent prospective observational study of adult abdominal pain patients presenting to large American urban EDs found the modified Alvarado rule at cutoff levels of 3, 4, and 5 had sensitivities of only 72%, 55%, and 36%, respectively, of ruling out the diagnosis.¹¹ In comparison, the study found that physicians’ clinical judgement of appendicitis being the first or second most likely diagnosis had a sensitivity of 93% for predicting appendicitis.¹¹

Comment: The Alvarado score was developed to help rule out and rule in the diagnosis of appendicitis. However, with the increasing availability of CT scanning in EDs, the diagnostic pathway in unclear cases has shifted from admission/observation to CT scanning, which has the benefit of elucidating other pathology as well. The utility of the Alvarado rule has been called into question. Ultimately, there is data in support of the Alvarado rule from older articles and studies in resource-poor environments, and newer studies may reflect less rigorous application of the rule when CT scanning is the default clinical pathway. Further studies that focus specifically on the Alvarado score as a rule out test to decrease CT utilization may be instructive.

Appendicitis Inflammatory Response (AIR) score

The appendicitis inflammatory response (AIR) score was derived in a cohort of 316 patients and validated on a sample of 229 adults and children with suspected appendicitis.12 The authors specifically sought to create a rule that outperformed the Alvarado score; the criteria are:

Vomiting: 1 point
Right iliac fossa pain: 1 point
Rebound tenderness: 1 point for light, 2 for medium, 3 for strong
Temperature >38.5°C: 1 point
Polymorphonuclear leukocytes: 1 point for 70%-84%, 2 for 85% or greater
White blood cell count: 1 point for 10,000-14,900, 2 for 15,000 or greater
C-reactive protein level (mg/dL): 1 point for 10-49, 2 for 50 or greater

Patients with a score of 0-4 were classified as low risk, with recommendation for outpatient follow-up if general condition unchanged; a score of 5-8 as indeterminate risk, with recommendation for active observation with serial exams, imaging, or diagnostic laparoscopy; or a score of 9-12 as high risk, with recommendation for surgical exploration.¹² In the validation cohort, the investigators found an AIR score or Alvarado score greater than 4 to have, respectively, 96% or 97% sensitivity and 73% or 61% specificity for detecting appendicitis.¹² A high score of greater than 8 on either the AIR or Alvarado had respectively 37% or 28% sensitivity but specificity of 99% for detecting appendicitis with either instrument.¹²