Which laboratory test would best indicate a developing systemic infection in a child whose mother reports drowsiness, poor appetite, and cough but has normal vital signs?

Which laboratory test would best indicate a developing systemic infection in a child whose mother reports drowsiness, poor appetite, and cough but has normal vital signs?

• A. Chest X-ray
• B. Urinalysis
• C. CBC with differential
• D. Serum electrolytes

Answer: (C)

When a child shows nonspecific symptoms like drowsiness, poor appetite, and cough with normal vital signs, a developing systemic infection may be present even before classic signs appear. The test that best captures this is a CBC with differential because it directly measures the body's immune response. It provides the total white blood cell count and the distribution of white cell types (neutrophils, lymphocytes, etc.). In the context of infection, you often see an elevated white blood cell count with a shift toward immature neutrophils (a left shift), indicating that the body is actively fighting an infection and a systemic process may be underway. The specific pattern can also give clues about whether the infection is more likely bacterial or viral, guiding further assessment and management. Chest X-ray can reveal pneumonia but does not by itself indicate a systemic infection. Urinalysis can detect a urinary tract infection but again focuses on a specific site rather than the overall systemic response. Serum electrolytes reflect hydration and electrolyte balance rather than infection status.

When a child shows nonspecific symptoms like drowsiness, poor appetite, and cough with normal vital signs, a developing systemic infection may be present even before classic signs appear. The test that best captures this is a CBC with differential because it directly measures the body's immune response. It provides the total white blood cell count and the distribution of white cell types (neutrophils, lymphocytes, etc.). In the context of infection, you often see an elevated white blood cell count with a shift toward immature neutrophils (a left shift), indicating that the body is actively fighting an infection and a systemic process may be underway. The specific pattern can also give clues about whether the infection is more likely bacterial or viral, guiding further assessment and management.

Chest X-ray can reveal pneumonia but does not by itself indicate a systemic infection. Urinalysis can detect a urinary tract infection but again focuses on a specific site rather than the overall systemic response. Serum electrolytes reflect hydration and electrolyte balance rather than infection status.