TABLE 2: Association of doubling ED or appendicitis volume and delayed diagnosis of appendicitis.

Model fit is shown using the Akaike information criterion (AIC). A null model with fixed intercept only had an AIC of 24139. Likelihood ratio tests (LRTs) compared each model to its parent; the parent of the volume models was the random intercept only model; the parents of the volume/patient models were the volume models. Model standard deviations (σ) describe the amount of between-ED variability in delayed diagnosis rates.

Model	Volume Effect, aOR (95% CI)	AIC	LRT p	Between-ED variability, σ (95% CI)	Between-ED variance explained, %
ED random intercept only		26460	<0.001	1.02 (0.95–1.11)	0
ED volume	0.93 (0.89, 0.98)	26454	0.005	1.00 (0.92–1.08)	5.1
ED volume and patient features	0.92 (0.87, 0.97)	25865	<0.001	1.05 (0.97–1.14)	−5.5
Appendicitis volume	0.76 (0.73, 0.79)	26310	<0.001	0.82 (0.75–0.89)	36.6
Appendicitis volume and patient features	0.74 (0.71, 0.77)	25709	<0.001	0.85 (0.78–0.93)	31.0