What laboratory finding is most consistent with an acute episode of bronchiolitis?

The presence of wheezing and crackles is the most consistent laboratory finding associated with an acute episode of bronchiolitis. Bronchiolitis is primarily caused by viral infections, most often respiratory syncytial virus (RSV), which leads to inflammation and obstruction in the small airways (bronchioles) of the lungs. This obstruction can result in wheezing, a high-pitched whistling sound during expiration, and crackles, which are indicative of fluid in the small airways or mucus. These sounds are typically noted during physical examination rather than through laboratory testing, but they are classic signs of the condition.

Increased respiratory rate may occur during an acute episode but is more of a physiological response to respiratory distress rather than a distinctive finding of bronchiolitis. Elevated blood glucose is not directly associated with the condition, and an increased white blood cell count might occur in various infections but does not specifically indicate bronchiolitis; in fact, we often see normal or even low white blood cell counts in viral infections. Thus, the presence of wheezing and crackles is a hallmark sign of bronchiolitis and directly reflects the underlying pathophysiology.