Which lab test can help identify respiratory infections in children?

The complete blood count (CBC) is a valuable lab test for identifying respiratory infections in children. It measures various components of blood, including white blood cells (WBCs), which play a key role in the immune response. An elevated WBC count, particularly an increase in neutrophils, may suggest a bacterial infection, while a higher lymphocyte count might indicate a viral infection. This test can help provide important clues about the underlying cause of respiratory symptoms in pediatric patients.

In contrast, the other options serve different purposes. Blood gas analysis primarily assesses the levels of oxygen and carbon dioxide in the blood and is used to evaluate the effectiveness of ventilation and oxygenation rather than directly identifying infections. Sputum culture is important for diagnosing infections, but it may not always be feasible in young children, especially those who cannot produce a sputum sample effectively. Pulmonary function tests are designed to measure lung function and airways but do not provide information on the presence of infections. Therefore, the CBC is an ideal initial test for evaluating potential respiratory infections in children.