A review on the relationship between C-Reactive protein (CRP) levels and the severity of COVID-19

Abstract

This review analyses data from 35 papers published between 2020 and 2024 to study the relationship between C-Reactive Protein (CRP) levels and the severity of COVID-19. Elevated CRP levels are consistently associated with more severe disease, including a high risk of respiratory failure, ICU admission, and fatality, across all study designs and groups. CRP is useful as an early indicator for clinical worsening since it rises early in the course of disease, frequently before radiological changes. Additionally, longitudinal data demonstrate that poor outcomes are highly predicted by rising CRP trends throughout hospitalisation. CRP remains one of the most useful, affordable and generally available indicators when compared to other inflammatory biomarkers such as CRP-derived ratios, including CRP/albumin and CRP/lymphocyte, which improve prognostic accuracy. The continuous correlation of CRP with unfavourable outcomes supports its utility in early risk stratification, particularly in situations with limited resources, even if it cannot entirely predict the severity of a disease on its own. To enhance future clinical applicability, standardisation of CRP readings and additional validation of cut-offs are advised.