Association of SP-A and SP-D Surfactant Proteins with the Severity of CommunityAcquired Pneumonia

Abstract

Relevance. In current clinical practice, there is a need for research to find new diagnostic tests for the purpose of determining the patients with the highest risk of death from pneumonia. Surfactant proteins SP-A and SP-D play a key role in the pathogenesis of the response to microbial invasion of lung tissue, which participate in a cascade of reactions of both innate and adaptive immunity, and therefore proteins SP-A and SP-D may be considered as markers of the severity of community-acquired pneumonia (CAP).Aim of study. To evaluate the associations of surfactant proteins SP-A and SP-D in blood plasma with the severity of CAP.Material and methods. The study included 247 patients admitted to the therapeutic department. The group of patients with CAP (n=188) was divided into groups of severe (n=103) and non-severe (n=85) pneumonia. The comparison group (n=59) consisted of patients without acute and chronic diseases of the bronchi and lungs. The mean age (years, Me, 25th; 75th percentile) of patients was 55 (47; 68), 55 (47; 70), and 61 (37; 63) years, respectively. All patients underwent clinical, functional, diagnostic and laboratory studies (including determination of the content of SP-A and SP-D proteins by enzyme immunoassay).Results. In the group of patients with severe pneumonia unlike mild pneumonia, and group of comparison higher levels of proteins SP-A and SP-D were observed. Correlation analysis described below revealed statistically significant connection: protein SP-D — direct relation with leukocyte levels (r=0.320, p<0.0001), erythrocyte sedimentation rate (r=0.331, p<0.0001), inverse relation with blood oxygen saturation (r=-0.407, p<0.0001), for SP-A protein — direct relation with body temperature (r=0.355, p<0.0001), erythrocyte sedimentation rate (r=0.369, p<0.0001) in the blood C-reactive protein (r=0.446, p<0.0001), SP-D (r=0.357, p<0.0001), and also relation with the duration of clinical symptoms (r=0.528, p<0.0001) and blood oxygen saturation (r=-0.401, p<0.0001). When conducting ROCanalysis for the surfactant protein SP-A, the area under the ROC- curve was 0.70, the optimal sensitivity for severe pneumonia was 68%, the specificity was 69% at the SP-A level in blood plasma equal to 42.9 ng/ml. When performing ROC analysis for the surfactant protein SP-D, the area under the ROC curve was 0.64 for severe pneumonia, the optimal sensitivity was 62%, and the specificity was 62% at the SP-D content in blood plasma equal to 319.2 ng/ml.Conclusion. According to the results of this study, the SP-A and SP-D proteins are associated with clinical and laboratory signs that reflect the severity of CAP. Thus, SP-A and SP-D are new laboratory markers of CAP severity.

Keywords

• surfactant
• surfactant protein a
• surfactant protein d
• biomarker
• community-acquired pneumonia