High levels in the C-reactive protein (CRP) test were found to be a helpful parameter in planning treatment for children with a diagnosis of respiratory syncytial virus (RSV) and a lower respiratory tract infection (LRTI), according to a study published in Viruses.

Although reverse transcriptase-polymerase chain reaction tests have been the preferred way to test for RSV, which is the most common cause of LRTI in infants and children across the world, blood count is emerging as a new way to determine systemic inflammation. Supportive treatments for infants and children with a diagnosis of RSV aim to reduce bronchoconstriction and inflammation, but a complete treatment is not yet available.

The study aimed to determine new markers of RSV infection activity in patients aged 0 to 12 years who had confirmed RSV through nasopharyngeal swab testing. The researchers evaluated the CRP, neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR), and the systemic immune-inflammation index (SII) to assess whether they could be used as an indicator of clinical utility in patients with RSV.

Participants in the study were stratified into 2 groups based on positive or negative RSV results. A total of 286 patients aged 0 to 12 years who were admitted to the Medicine Hospital Istanbul Atlas University in Turkey between January 1, 2020, and January 1, 2022, were included in the study. Of these patients, 138 were RSV positive, and 148 were RSV negative.

Children were included if they had consulted a clinician and were less than 12 years of age. Children were excluded if they had a history of wheezing, had serious comorbidities, had neurological and metabolic disorders, immune deficiency, recurrent infections of RSV, or were older than 12 years of age. RSV was diagnosed using a nasopharyngeal swab sample. Complete blood count (CBC) was assessed with a hematology analyzer and CRP levels were measured with the nephelometric method.

The median (IQR) lymphocyte count was found to be 4.34 (2.65-6.36) in the RSV positive group and 2.78 (1.4-3.6) in the RSV negative group. CRP was also found to be higher in the RSV positive group compared with the RSV negative group (4.59 [2.57-13.63] vs 0.72 [0.55-1.25]).

The RSV-positive group had significantly lower NLR (0.81 [0.41-1.64] vs 1.37 [1.08-2.16]), PLR (72.17 [49.63-108.26] vs 119.31 [90.32-223.07]), and SII (243.40 [127.03-554.42] vs 449.5 [349.25-622]) compared with the RSV negative group. For children less than 2 years of age, white blood count, lymphocytes, CRP, NLR, PLR, and SII were all different between the RSV positive and negative groups. CRP was the only significant factor between the groups in children aged 2 years or more.

This study was conducted in a single-center, was retrospective, and was only conducted on a limited number of cases, all of which the authors noted as limitations.

The researchers concluded that CRP values were better as markers for RSV compared with other blood parameters. High levels of CRP could be a helpful parameter when planning treatment processes, especially in children who are aged 2 years and older.

"Our study may be an inspiration for investigating the effect of other inflammatory parameters, such as the hematological index, on RSV infection," the authors wrote. "RSV infection is a health problem and may be associated with asthma as the patient ages. At the same time, it is still not possible to give a clear lower and upper limit for the new-generation inflammation markers used in our study in healthy children. Therefore, there is a need for long-term studies that include long-term observation of patients with RSV."


Okuyan O, Elgormus Y, Dumur S, Sayili U, Uzun H. New generation of systemic inflammatory markers for respiratory syncytial virus infection in children. Viruses. 2023;15:1245. doi:10.3390/v15061245

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