Approach to a fever (over 2 months): Clinical sciences

Fever is defined as a temperature of 38 degrees Celsius or 100.4 degrees Fahrenheit, or higher. It’s crucial to determine the source of fever in children over 2 months of age in order to promptly identify the cause of the fever and initiate appropriate treatment. The most important underlying causes of fever include infection, malignancy, inflammatory conditions, and certain medications.

If a child over 2 months of age presents with a fever, you should first perform an ABCDE assessment. If the patient is unstable, stabilize the airway, breathing, and circulation. Next, obtain IV access, and consider starting IV fluids. Finally, put your patient on continuous vital sign monitoring, including blood pressure, heart rate, and oxygen saturation, and provide supplemental oxygen if needed.

Okay, now let’s go back to the ABCDE assessment and look at stable patients. First, let’s start by obtaining a focused history and physical exam. The presence of a temperature of 38 degrees Celsius or higher confirms a fever, so your next step is to assess signs and symptoms of a clinical infection.

First, let’s start with signs and symptoms that suggest a localized infection, such as a purulent middle ear effusion, tonsillar exudates, focal crackles on lung auscultation, or a history of dysuria with urinary urgency or frequency. If this is the case, consider ordering additional testing, like a urinalysis and urine culture, chest X-ray, rapid strep test, or throat culture. If the confirmatory testing identifies a focus of infection, or if you’re able to make a clinical diagnosis based on exam findings alone, you can diagnose a focal infection. Some common examples of focal bacterial infections in children include otitis media, urinary tract infection, pneumococcal pneumonia, and group A Strep pharyngitis.

On the other hand, in some individuals, you might identify signs and symptoms suggesting a systemic infection, such as malaise, fatigue, weakness, chills, muscle or joint pain, and decreased appetite. In this case, you can consider diseases like influenza, enterovirus, Lyme disease, blastomycosis, or malaria; and order additional tests to confirm the diagnosis, such as serology, nucleic acid amplification testing, or cultures. If confirmatory testing identifies a cause of systemic infection, or if you are able to make a clinical diagnosis based on findings alone, you can diagnose systemic infection.

Now, if you identify no signs or symptoms of infection, your next step is to assess your patient’s age and body temperature.

If your patient is between 2 and 36 months of age, with a temperature of 39 degrees Celsius or higher, you should consider an occult bacterial infection. Start by ordering labs, including a CBC, procalcitonin or CRP, and urinalysis. Additionally, consider obtaining blood and urine cultures, and depending on other patient factors, consider sending cerebrospinal fluid, or CSF, for analysis and culture.

Now, if there’s an occult bacterial infection, the CBC might reveal elevated WBCs with neutrophilia in combination with an elevated PCT or CRP. The urinalysis may also reveal the presence of WBCs with a positive leukocyte esterase, and if obtained, the CSF analysis may show pleocytosis. These findings are highly suggestive of a bacterial infection, so while you’re waiting for culture results, consider hospital admission and empiric treatment with antibiotics.

Next, review the culture results once they are available. If the CSF culture is positive, you can diagnose bacterial meningitis; if the urine culture is positive, diagnose UTI; and if the blood culture is positive, you can diagnose bacteremia.

Finally, if all cultures are negative, you should discontinue antibiotics and continue to look for an underlying cause of fever. In this case, your next step is to assess for signs and symptoms of malignancy!

Similarly, for febrile children over 36 months of age, and those between 2 and 36 months of age with a temperature between 38 and 39 degrees Celsius, you should assess for signs and symptoms of malignancy.

Some important signs and symptoms suggesting malignancy include weight loss, fatigue, or night sweats, as well as pallor, hepatosplenomegaly, and lymphadenopathy. The presence of any of these findings in combination with fever should make you consider malignancy, such as leukemia and lymphoma. In these individuals, your next step is to order labs, including a CBC with a peripheral smear; and obtain bone marrow or lymph node biopsy. Finally, if your patient reports respiratory symptoms, consider ordering a chest X-ray.

Patients with leukemia often report fatigue, bleeding, and bone pain; while the physical exam may be significant for pallor, bruising, or petechiae. The CBC usually demonstrates leukocytosis and anemia, while peripheral smear and bone marrow biopsy reveal the presence of immature blasts. With these findings, you can diagnose leukemia.

Meanwhile, individuals with lymphoma often report night sweats, weight loss, and occasionally, they may also have dyspnea or a cough; while the physical exam commonly reveals lymphadenopathy or hepatosplenomegaly. A lymph node biopsy demonstrates the presence of malignant cells, while the chest X-ray may show a mediastinal mass. With these findings, you can diagnose lymphoma.