To determine the severity of a respiratory infection in children who regularly suffer from it, it is better to examine their saliva instead of their blood. This is the conclusion of researchers from Radboudumc Nijmegen, UMC Utrecht, and Wilhelmina Children's Hospital, among others, after a study of a hundred children who suffer from recurring respiratory infections. According to them, saliva measurements provide a better indication of the seriousness of the disease than measurements in the blood. Moreover, such measurements are more pleasant for children.

According to the researchers, about 10 to 15 percent of all children have to deal with recurring respiratory tract infections, often caused by a virus or bacteria. If children end up in the hospital with this, blood is drawn to look for antibodies and possible underlying conditions or causes. However, according to the researchers, this rarely yields results. That is why the hospitals looked for alternatives.

The researchers found no connection between blood substances and the infection's severity in the blood tests. "But in saliva, we saw very broad protective antibodies, which work against various pathogens," said PhD candidate Mischa Koenen. "Children with fewer antibodies do worse and get more serious infections. These substances are, therefore, a good indication of disease burden." For example, children with few broad protective antibodies in their saliva get pneumonia more often.

Researchers also discovered that a particular bacterium on the mucous membrane in the nasopharynx is also related to the severity of a respiratory infection. Children who have a lot of this bacterium, which is also found in healthy airways, on their mucous membranes are much more often ill in the winter, the researchers concluded.