The primary objective was to compare serum interleukin-1 receptor antagonist (IL-1RA) levels in cases of community acquired pneumonia (CAP) and healthy age-gender-matched controls. The secondary objective was to compare serum IL-1RA levels in cases which were positive or negative for Streptococcus pneumoniae in the blood by real-time-polymerase chain reaction (RT-PCR). Hospitalized children with World Health Organization defined CAP, aged 2-59 months, were included as cases. Healthy controls were recruited from the immunization clinic of the hospital. Enzyme-linked immunosorbent assay (ELISA) test was used to detect serum IL-1RA levels. Identification of S.pneumoniae in blood was done by RT-PCR. From October 2019 to October 2021, 330 cases (123, 37.27% female) and 330 controls (151, 45.75% females) were recruited. Mean serum IL-1RA levels (ng/ml) were 1.36 ± 0.95 in cases and 0.25 ± 0.25 in controls (p < 0.001). Within cases, serum IL-1RA levels were significantly higher in those whose RT-PCR was positive for S.pneumoniae. Thus serum IL-1RA levels may be evaluated as a surrogate marker of S.pneumoniae in future studies.
Keywords: Streptococcus pneumoniae; community acquired pneumonia; interleukin-1 receptor antagonist; real-time-polymerase chain reaction; variable number of tandem repeats.
The main purpose of the study was to compare the levels of a protein in the blood that is part of the immune system, called interleukin-1 receptor antagonist (IL-1RA) which binds to the same site in the body as an antibody does when it is fighting certain diseases, like pneumonia. We then compared the levels of this protein, IL-1RA, in hospitalized cases of community acquired pneumonia (CAP), caused from exposure to germs in the community, rather than obtained or contracted in a hospital, to that found in healthy people or ‘controls’ recruited from an immunization clinic. Cases and controls were matched for age and gender. The secondary objective of our study was to compare the level of IL-1RA protein in the blood in cases that were positive for the bacteria Streptococcus pneumoniae measured in the blood by a molecular test called real-time-polymerase chain reaction which can detect a very small amounts of a protein that is uniquely found in the S.pneumoniae bacteria that causes CAP. This case–control study was conducted in a large teaching institution that receives referrals from the other hospitals in northern India. It was found that serum IL-1RA levels were raised in cases of CAP, especially those which were possibly due to S.pneumoniae.
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