Association of the novel CROW-65 risk score and mortality in hospitalized kidney transplant recipients with COVID-19

Kidney transplant recipients (KTR) are a group of patients with heterogeneous risks for adverse outcomes with COVID-19, but risk stratification tools in this patient group are lacking.

This retrospective observational, hypothesis-generating study included 49 hospitalized adult KTR patients with COVID-19 at the University Hospital of Split (August 2020 to October 2021) and evaluated the performance of novel risk score CROW-65 (age, Charlson Comorbidity Index [CCI] lactate dehydrogenase to white blood cell [LDH:WBC] ratio, and respiratory rate oxygenation [ROX index]). The primary outcome of the study was 30-day postdischarge all-cause mortality.

A total of 8 fatal events (16.3%) occurred during the study follow-up. When comparing CROW-65 by survival status, it was significantly increased in patients with fatal event (P < 0.001). Using the Cox proportional hazards regression analysis, the CROW-65 risk score showed statistically significant association with mortality (HR 1.11, 95% CI 1.01–1.23, P = 0.027), while receiving operator characteristics (ROC) showed significant discrimination of all-cause mortality with an AUC of 0.85 (95% CI 0.72–0.94, P < 0.001), and satisfactory calibration (χ² 4.91, P = 0.555 and Harrell’s C 0.835). Finally, survival Kaplan-Meier analysis confirmed significantly higher cumulative incidence of mortality with increasing risk score tertiles and curve separation after 13 days (P = 0.009).

A novel risk score CROW-65 showed significant association with all-cause mortality in KTR yielding important hypothesis-generating findings. Further powered studies should reassess the performance of CROW-65 risk score in this population, including predictability, calibration and discrimination.