A risk score system for predicting complicated appendicitis and aid decision-making for antibiotic therapy in acute appendicitis

Background: Exclusive antibiotic therapy is a feasible treatment option for uncomplicated appendicitis, but the pre-treatment diagnosis of uncomplicated appendicitis is challenging. This study aimed to develop a risk score system to predict complicated appendicitis and aiding decision-making regarding antibiotic therapy for acute appendicitis.

Methods: The risk score system for predicting complicated appendicitis was constructed and validated by a surgical therapy cohort (n=543). Furthermore, we applied an independent antibiotic treatment cohort (n=169) to verify whether the risk score system could guide antibiotic treatment decision-making in patients with acute appendicitis (AA).

Results: A total of 543 patients were included in the surgical therapy cohort and was split into the primary (n=375) and validation (n=168) cohorts with repeated random sampling. In the primary cohort, multivariate analysis confirmed that periappendiceal fat stranding (PFS, P<0.001, OR =67.80), the C-reactive protein level (CRP ≥38 mg/L, P<0.001, OR =5.77) and the neutrophil-to-lymphocyte ratio (NLR ≥7, P<0.001, OR =3.51) were independent risk factors for complicated appendicitis. The PFS, CRP and NLR scores were 10.0, 4.0 and 3.0 points, respectively. Fourteen patients (3.7%, 14/375) and seven patients (4.2%, 7/168) with pathologically confirmed complicated appendicitis were classified as having uncomplicated appendicitis in the primary and validation cohorts based on the risk score system, respectively. In the independent antibiotic treatment cohort (n=169), the failure rate of antibiotic treatment was 49.2% and 5.3% for the risk score system predicted complicated AA and uncomplicated AA. Furthermore, the predictive accuracy of the risk score system for antibiotic treatment failure as measured by the area under the curve (AUC) was 0.823 (95% CI: 0.757-0.878).

Conclusions: We found that the proposed risk score system based on biological and CT features not only enables the accurate identification of complicated appendicitis patients before pre-treatment but also serves to guide antibiotic treatment decisions.