What initial diagnostic test should be ordered for a 12-year-old girl suspected of having community-acquired pneumonia?

In the case of a 12-year-old girl suspected of having community-acquired pneumonia (CAP), ordering a complete blood count (CBC) with differential serves as a valuable initial diagnostic tool. The CBC can help identify the presence of infection by revealing elevated white blood cell counts, which are typically indicative of an inflammatory response. This can provide supporting evidence for the diagnosis of pneumonia, as well as help in assessing the severity of the illness.

Furthermore, the differential can give insights into whether the infection is more likely to be viral or bacterial, based on the types of white blood cells elevated. For instance, a predominance of neutrophils often suggests a bacterial infection, while lymphocytic predominance may point to a viral cause.

Other tests, such as sputum cultures, are more invasive and not typically necessary at the initial evaluation, especially if clinical signs and symptoms are strong enough to support a diagnosis of CAP. Additionally, serum procalcitonin is a marker that can indicate bacterial infection, but it’s not routinely used in standard practice for initial workup in mild to moderate pneumonia cases. In many instances, clinical observations and the patient’s history can guide the diagnosis effectively without requiring extensive laboratory tests. Therefore, while a variety of tests may