The diagnosis is typically made by clinical examination. Chest X-ray is sometimes useful to exclude bacterial pneumonia, but not indicated in routine cases. Chest x-ray may also be useful in people with impending respiratory failure. Additional testing such as blood cultures, complete blood count, and electrolyte analyses are not recommended for routine use although may be useful in children with multiple comorbidities or signs of sepsis or pneumonia. Testing for the specific viral cause can be done but has little effect on management and thus is not routinely recommended. RSV testing by direct immunofluorescence testing on nasopharyngeal aspirate had a sensitivity of 61% and specificity of 89%. Identification of those who are RSV-positive can help for disease surveillance, grouping ("cohorting") people together in hospital wards to prevent cross infection, predicting whether the disease course has peaked yet, and reducing the need for other diagnostic procedures (by providing confidence that a cause has been identified). Identification of the virus may help reduce the use of antibiotics. Infants with<unk>  between the age of two and three months have a second infection by bacteria (usually a urinary tract infection) less than 6% of the time. When further evaluated with a urinalysis, infants with<unk>  had a concomitant UTI 0.8% of the time. Preliminary studies have suggested that elevated procalcitonin levels may assist clinicians in determining the presence of bacterial co-infection, which could prevent unnecessary antibiotic use and costs. Differential diagnosis There are many childhood illnesses that can present with respiratory symptoms, particularly persistent cough and wheezing.<unk>  may be differentiated from some of these by the characteristic pattern of preceding febrile upper respiratory tract symptoms lasting for 1 to 3 days followed by the persistent cough, tachypnea, and wheezing. However, some infants may present without fever (30% of cases) or may present with apnea without other signs or with poor weight gain prior to onset of symptoms. In such cases, additional laboratory testing and radiographic imaging may be useful. The following are some other diagnoses to consider in an infant presenting with signs of<unk> : * Asthma and reactive airway disease * Bacterial pneumonia * Congenital heart disease * Heart failure * Whooping cough *Allergic reaction * Cystic fibrosis *Chronic pulmonary disease * Foreign body aspiration * Vascular ring
Bronchiolitis
Heart failure
Bronchitis
Asthma
Bronchitis kettle
Pneumonia
Croup
Cystic fibrosis