INVESTIGATIONS
Children with bacterial pneumonia cannot be reliably distinguished from those with
viral disease on the basis of any single parameter; clinical, laboratory or chest
radiograph findings.
1. Chest radiograph
Chest radiograph is indicated when clinical criteria suggests pneumonia. It will not
identify the aetiological agent. However the chest radiograph is not always necessary if
facilities are not available or the pneumonia is mild13
2. Complete white blood cell and differential count
This test may be helpful as an increased white blood count with predominance of
polymorphonuclear cells may suggest bacterial cause. However, leucopenia can either
suggest a viral cause or severe overwhelming infection. 14
3. Blood culture
Blood culture remains the non-invasive gold standard for determining the precise
aetiology of pneumonia. However the sensitivity of this test is very low. Positive blood
cultures are found only in 10% to 30% of patients with pneumonia15. Even in 44% of
patients with radiographic findings consistent with pneumonia, only 2.7% were positive
for pathogenic bacteria.16 Blood culture should be performed in severe pneumonia or
when there is poor response to the first line antibiotics.
4. Culture from respiratory secretions
It should be noted that bacteria isolates from throat swabs and upper respiratory tract
secretions are not representative of pathogens present in the lower respiratory tract.
Samples from the nasopharynx and throat have no predictive values.6 This investigation
should not be routinely done.
5. Other tests
Bronchoalveolar lavage is usually necessary for the diagnosis of Pneumocystis carini
infections primarily in immunosuppressed children. It is only to be done when facilities
and expertise are available.