ACR Appropriateness Criteria®
Clinical Condition: Fever without Source (FWS)
Variant 1: Infant or child greater than one month of age with no respiratory signs or symptoms.
| Radiologic Exam Procedure |
Appropriateness Rating |
Comments |
| X-ray, chest |
2 |
|
Appropriateness Criteria Scale
1 2 3 4 5 6 7 8 9
1 = Least appropriate 9 = Most appropriate
|
Variant 2: Child with cancer and neutropenia. No respiratory signs or symptoms.
| Radiologic Exam Procedure |
Appropriateness Rating |
Comments |
| X-ray, chest |
3 |
|
Appropriateness Criteria Scale
1 2 3 4 5 6 7 8 9
1 = Least appropriate 9 = Most appropriate
|
The febrile pediatric patient, especially an infant, represents a dilemma for the primary care physician. The source of the fever can vary from a brief, minor illness to a life-threatening infection and often cannot be found despite a careful history and physical examination. Fever without source (FWS) or fever without localizing signs (FWLS) is an acute febrile illness of which the origin of the fever is not apparent after initial careful history and examination. The term fever of unknown origin (FUO) generally refers to a fever lasting two weeks or more without an apparent etiology, but the definition of FUO remains controversial. Other investigators have used 7 to 10 days of fever rather than two weeks to define FUO. The definition of fever is generally regarded as a rectal temperature of 38 degrees centigrade or higher. Oral temperatures are fairly unreliable, although they are the usual method of measuring temperature in older children and adults.
The cause of fever in the pediatric patient can often be determined from the history, physical examination, and laboratory tests. A thorough history is important as medications, foreign travel, pets, or prior illnesses could direct the clinical investigation and imaging to the fever cause, as could awareness of prior abdominal inflammation processes such as Crohns, recent surgery for appendicitis, etc. The yield from the physical examination is not recorded in most studies of FUO other than to note that diagnostic testing was guided by the physical examination. Two studies report that almost 60% of the patients examined had abnormal findings that contributed to the eventual diagnosis. Traditionally, febrile infants younger than three months are hospitalized. The cerebral spinal fluid is examined, the blood and urine are cultured for pathogens, and empiric antibiotics are given. In addition, a chest radiograph has been part of most protocols and practices. Hospitalization for all febrile infants in the first several months of life has been shown to be an expensive management strategy and can incur significant iatrogenic complications. The infants in this category have somewhere between 3% to 10% incidence of what would be designated as a serious bacterial infection (SBI). Two clinical protocols such as the Rochester Criteria and the Milwaukee Criteria, along with various laboratory tests, have been offered to help determine the probability of an SBI in infants with a febrile illness. The use of strict screening criteria can permit a substantial number of febrile one- to two-month-old infants to be treated as outpatients and without antibiotics.
How often noninvasive testing has provided a diagnosis in FUO cases is difficult to determine. In adults it is stated to be perhaps one quarter. An example of serological testing that could lead to a diagnosis would be in generalized systemic Bartonella henselae where children seem to be prone to develop prolonged fever.
For infants who have fever and chest symptoms, most investigators feel that chest radiographs are indicated and are useful. Therefore, an infant with bronchiolitis or upper respiratory infection does not have a true FWS or FWLS. Clinical factors predictive of pneumonia in children of all ages have been studied. The presence of rales is the single best clinical indicator of pneumonia in infants and children. Tachypnea and fever are also predictive findings for pneumonia in the pediatric population.
One study recommends that chest radiographs be obtained only in patients 3 through 36 months of age with fever when there are clinical manifestations of chest disease or when the patient appears toxic. This same study reported a 3.3% incidence of positive chest radiographs based on collected reviews of infants and children from birth to 36 months of age with fever and no respiratory symptoms or signs. A different researcher, summarizing a number of clinical series dealing with acute episodes of fever in infants, also believes that chest radiographs should be obtained only when there are clinical indications. Another study combined data of three investigations and subjected them to a statistical meta-analysis by using methods described in recent medical literature. The larger number of patients in the combined study allowed more valid conclusions concerning the accepted practice of performing chest radiographs in febrile infants as part of the sepsis workup. These three series had 671 infants. In 361 infants with no clinical evidence of pulmonary disease on history and physical examination, all had normal chest radiographs. A finding of only hyperinflation on a chest radiograph was interpreted as normal because it was felt that the infants would likely have a viral illness or reactive airway disease and would not usually be receiving antibiotics, unlike older children and adults. This study indicated that a chest radiograph in a patient with no pulmonary symptoms or signs would be positive <1.2% of the time. In the same series, nearly one-third of 256 infants with clinical manifestations of pulmonary disease had a positive chest radiograph; therefore, in symptomatic, febrile infants, a chest radiograph can help identify significant pulmonary disease and should be obtained.
One group of researchers retrospectively studied 105 infants who had fever. Of the 37 patients who had no respiratory symptoms or signs, there was one chest radiograph that showed a focal parenchymal infiltrate. Hyperinflation and peribronchial thickening were not classified as abnormal. In a prospective study the same authors included 121 infants who were free of signs of lower tract respiratory symptoms and signs but who had fever. None had chest radiographs that showed an abnormality. These data suggest that obtaining chest radiographs to look for parenchymal infiltrates treatable by antibiotics for infants less than two years old is necessary only in those infants who have clinical evidence of lower respiratory illness. Another study concluded that in febrile infants younger than three months of age, a chest radiograph should be obtained only when signs of respiratory disease are present. In this series the incidence of pneumonia in infants without respiratory manifestations was 6%, and all those infants did well, having only mild infiltrates on their chest radiographs. The case for not obtaining chest radiographs in the absence of pulmonary clinical manifestations also applies to the pediatric population beyond infancy but is not as well documented as in infants.
A child with cancer who is febrile and neutropenic is often evaluated with a chest radiograph in addition to other assessments, including cultures of the blood and urine. The practice of routinely including a chest radiograph has been challenged by investigators who point out that the incidence of pneumonia is low with fever and neutropenia. The rate is between 3 to 6% and is still lower in children with no respiratory symptoms. In one study, 54 children with cancer were hospitalized for hundreds of episodes of fever and neutropenia, and the children without respiratory findings had no evidence of pneumonia on chest radiographs. In the same study, children who did not have chest radiographs showed no significant outcome differences from those who did. In patients with fever lasting longer than three weeks without localizing signs or symptoms, special imaging studies such as computed tomography (CT) or ultrasound rarely lead to a diagnosis. In patients with fever for more than three weeks and no localizing clinical findings, gallium 67 scanning is of little value. Indium-111 granulocyte scintigraphy performed better than fluorine-18 fluorodeoxyglucose in adults.
Most investigators feel that a chest radiograph should remain part of a sepsis evaluation in the neonate. Some will obtain a chest radiograph in a septic appearing pediatric patient without an apparent focus of infection because the radiograph may disclose an occult (pleural, parenchymal, or pericardial) source of the fever. In addition, a chest radiograph will help exclude congenital or acquired cardiac disease in a child who is febrile and ill.
Most data support the opinion that chest radiographs in the febrile patient should be obtained only when there is clinical evidence of a respiratory illness. One should be able to assess the cost benefit and risk benefit ratios for each test. In the case of radiologic evaluation the cost and risk of radiation exposure, albeit small, must be weighed against the diagnostic information provided. The incidence of serious bacterial infection (SBI) is low but does prompt costly evaluations in infants with FWLS. Clinical variables are guidelines for the physician, not a substitute for overall clinical judgment in the decision of which febrile infants and children would benefit from chest radiographs. When a child with an FUO is in a hospital setting, a sonogram or CT of the abdomen may be requested in addition to a chest radiograph. CT of the chest may also be requested. If the patient is immune compromised, these imaging requests are even more frequent. Data supporting these approaches are lacking, which is not to say that they are inappropriate but rather that they lack good documentation of their value.
