Clinical and prognostic significance of C-reactive protein to albumin ratio in hospitalized coronavirus disease 2019 (COVID-19) patients

C‑reactive protein (CRP) and albumin are inflammation sensitive parameters that are regulated by interleukin‑6 inflammatory pathways. The CRP to albumin ratio (CAR) integrates these two into a potent clinical parameter whose clinical and prognostic association in the context of coronavirus disease 2019 (COVID-19) have not been well defined. We aimed to investigate the clinical and prognostic significance of CAR in the context of COVID-19 infection.

We retrospectively analyzed 2309 consecutive COVID-19 patients hospitalized at a tertiary level hospital in the period from March 2020 to March 2021 who had baseline data for a CAR assessment. Findings were validated in an independent cohort of 1155 patients hospitalized from March 2021 to June 2021.

The majority of patients (85.8%) had severe or critical COVID-19 on admission. Median CRP, albumin and CAR levels were 91 mg/L, 32 g/L and 2.92, respectively. Higher CAR was associated with a tendency for respiratory deterioration during hospitalization, increased requirement of high-flow oxygen treatment and mechanical ventilation, higher occurrence of bacteriemia, higher occurrence of deep venous thrombosis, lower occurrence of myocardial infarction, higher 30-day mortality and higher postdischarge mortality rates. We defined and validated four CAR prognostic categories (< 1.0, 1.0–2.9, 3.0–5.9 and ≥ 6.0) with distinct 30-day survival. In the series of multivariate Cox regression models we could demonstrate robust prognostic properties of CAR that was associated with inferior 30-day survival independently of COVID-19 severity, age and comorbidities and additionally independently of COVID-19 severity, CURB-65 and VACO index in both development and validation cohorts.

The CAR seems to have a good potential to improve prognostication of hospitalized COVID-19 patients.