What clinical variables help distinguish pelvic inflammatory disease from acute appendicitis in women?

In this poorly described study, a clinical decision rule consisting of 3 variables helped distinguish appendicitis from pelvic inflammatory disease (PID) in women of childbearing age: no pain migration; bilateral tenderness; and no nausea and vomiting. This rule needs to be validated. (LOE = 3b)

Morishita K, Gushimiyagi M, Hashiguchi M, Stein GH, Tokuda Y. Clinical prediction rule to distinguish pelvic inflammatory disease from acute appendicitis in women of childbearing age. Am J Emerg Med 2007;25:152-157.  [PMID:17276803]

Decision rule (development only)

Unknown/not stated

Emergency department

These authors retrospectively assessed the medical records of 181 consecutive women between the ages of 12 years and 58 years of age presenting to the emergency department for the evaluation of acute abdominal pain. They don't describe how they extracted the data from the medical records or if the original clinical information was collected in a standard fashion or if the final diagnoses were made using standardized criteria. The final diagnosis of appendicitis was determined by histopathologic findings. PID was established using the Centers for Disease Control's minimum criteria: lower abdominal tenderness, adnexal tenderness, and cervical motion tenderness. Three clinical factors were more likely to be associated with a low risk of appendicitis: no pain migration; bilateral tenderness; no nausea and vomiting. Combining these into a prediction model was 99% sensitive (95% CI, 94.4-99.9) for ruling out appendicitis, but only 33.9% specific (23.1-46.6). The positive likelihood ratio was 1.5 (1.25-1.80) and the negative likelihood ratio was 0.03 (.004-.22). This means the clinical criteria were very good at ruling out appendicitis but not good at ruling it in.