The predictive value of serum amyloid A and C-reactive protein levels for the severity of coronavirus disease 2019

Am J Transl Res. 2020 Aug 15;12(8):4569-4575. eCollection 2020.


This study was designed to assess the levels of human serum amyloid A (SAA) and C-reactive protein (CRP) in patients with coronavirus disease 2019 (COVID-19) to determine their prognostic value in predicting the severity of disease. Patients with COVID-19 who presented with acute respiratory distress syndrome (ARDS) shared distinct characteristics. For example, the patients were older, and had higher levels of inflammatory indicators [i.e., levels of CRP, SAA, procalcitonin (PCT), and interleukin-6; CRP-to-PCT ratio; SAA-to-CRP ratio; and neutrophil-to-lymphocyte ratio (NLR)], higher inflammatory cell counts (i.e., white blood cell count and neutrophil count), and lower lymphocyte counts compared with patients without ARDS. Patients without ARDS still exhibited mild illness and had elevated SAA levels but not CRP levels. In patients with elevated SAA and CRP levels, the NLR was statistically associated with disease severity. According to the receiver operating characteristic curve analysis, the combined predictive probability of CRP and SAA levels, along with white blood cell count, showed the highest area under the curve (AUC; 0.878), and was able to distinguish between patients with and without ARDS. The cut-off level for SAA to predict the severity of COVID-19 was 92.900, with a sensitivity of 95.8%, a specificity of 53.7%, and an AUC of 0.712. For patients with elevated levels of SAA but not CRP, a mild condition was predicted. For patients with elevated levels of both SAA and CRP, and a high NLR, a severe infection was predicted, requiring medical attention. Therefore, CRP and SAA levels demonstrate a prognostic value for predicting the severity of COVID-19.

Keywords: CRP; Coronavirus disease 2019 (COVID-19); human SAA; neutrophil-to-lymphocyte ratio; procalcitonin.