Prognostic validation of a simplified chest CT severity score in COVID-19 patients from resource-limited Gaza

To validate the Simplified Chest CT Severity Score (SCCTSS) for prognostic stratification of COVID-19 pneumonia in a resource-limited Gaza cohort and compare its diagnostic accuracy and interobserver reliability against the established Chest CT Score (CCTS).

In this retrospective cohort study, 360 adult patients with RT-PCR-confirmed COVID-19 underwent non-contrast chest CT within 72 h of admission (September 2020-June 2022). SCCTSS assessed three parameters, opacity type, extent, and distribution, with scores ranging from 0 to 7 and classified into no involvement (0), mild (3), moderate (4-5), and severe (6-7) disease. CCTS scores ranged from 0 to 25 and were categorized as no involvement (0), mild (1-8), moderate (9-16), and severe (17-25). Interobserver agreement was measured by Cohen's kappa. Diagnostic accuracy for mortality prediction was evaluated via sensitivity, specificity, ROC curves, and Kaplan-Meier survival analyses.

SCCTSS demonstrated almost perfect interobserver reliability (κ = 0.883), comparable to CCTS (κ = 0.870). Mortality was significantly associated with higher SCCTSS categories; 58.5% of non-survivors had severe scores (6-7), compared to 3.7% of survivors (p < 0.001). At the optimal cutoff (≥ 3.5), SCCTSS sensitivity was 93.2%, specificity 90.1%, with AUC 0.933. CCTS (cutoff ≥ 8.5) showed 89.8% sensitivity, 93.4% specificity, and AUC 0.948. Kaplan-Meier analysis confirmed significantly reduced 30-day survival in patients with scores above these thresholds (p < 0.001).

SCCTSS is a simple, reproducible, and effective CT scoring tool for COVID-19 prognostication, suitable for rapid risk stratification in resource-limited environments.