Respiratory infections in kids better detected with saliva tests than blood tests

New Delhi: A new study published on Thursday demonstrates that saliva tests are a more reliable indicator of the severity of recurring respiratory infections in children than the typical blood test.

Researchers from UMC Utrecht Wilhelmina Children's Hospital and Radboudumc Amalia Children's Hospital in the Netherlands conducted the study, which shows a correlation between a child's risk of pneumonia episodes and low levels of broadly protective antibodies in their saliva.

This method offers valuable diagnostic information and is more comfortable for children.

Recurrent respiratory infections affect 10-15 per cent of children. Typically, paediatricians rely on blood tests to identify antibody deficiencies as an underlying condition, though these tests often yield limited results.

"This is challenging for paediatricians because we really want to help the children," said Dr Lilly Verhagen, paediatric infectious disease specialist at Radboudumc.

"We explored whether saliva testing could better indicate disease severity, which would help determine which children need more intensive care or antibiotic treatment," she added.

The study, which involved 100 children with recurrent respiratory infections, found that saliva measurements were more effective than blood tests in indicating disease severity.

"We observed no correlation between blood antibodies and disease burden, but saliva revealed broadly protective antibodies that combat a range of pathogens. Children with lower levels of these antibodies experienced more severe infections," explained Mischa Koenen, doctoral student at UMC.

These broadly protective antibodies are abundant in the airways and were also found in the saliva of healthy siblings, parents, and caregivers. Researchers discovered that even pre-pandemic children's saliva contained antibodies capable of binding to the SARS-CoV-2 virus, the virus responsible for the Covid-19 pandemic.

The study also explored the role of the airway microbiome, identifying Haemophilus influenzae as a bacterium strongly associated with severe respiratory infections. Children with high levels of this bacterium were more frequently ill during winter.

Future assessments may incorporate saliva and nasopharyngeal mucosal measurements to better evaluate children's care needs. This approach could lead to more effective treatments and child-friendly diagnostic practices, potentially replacing some follow-up blood tests, the team said.