Investigations in Pediatric Pneumonia
Chest X-Ray (CXR) — Primary Investigation
- Most important investigation in suspected pneumonia
- Guides diagnosis, monitors response, detects complications
- See Pediatric Pneumonia CXR Patterns for detailed pattern descriptions
When to request CXR:
- All hospitalized children with suspected pneumonia
- Severe or complicated cases
- Poor response to treatment
- Recurrent pneumonia (evaluate underlying cause)
Complete Blood Count (CBC)
| Finding | Interpretation |
|---|---|
| Leukocytosis (neutrophilia) | Bacterial pneumonia (pneumococcal, staphylococcal, H. influenzae) |
| Normal / slightly elevated WBC | Viral pneumonia, Mycoplasma |
| Eosinophilia | Loeffler syndrome (larval migration); also consider Chlamydia trachomatis |
| Leukopenia | Severe bacterial infection, viral pneumonia |
Inflammatory Markers
| Marker | Use |
|---|---|
| CRP (C-reactive protein) | Elevated in bacterial pneumonia; helps differentiate from viral |
| Procalcitonin (PCT) | Better specificity for bacterial infection; guides antibiotic stewardship |
| ESR | Non-specific; elevated in bacterial infection |
Blood Culture
- Positive in only 5–10% of pneumococcal pneumonia cases
- Higher yield in staphylococcal and H. influenzae pneumonia (bacteremia-associated)
- Essential in all hospitalized / severe pneumonia cases
- Taken before starting antibiotics
Sputum Examination
- Difficult to obtain in young children
- Gram stain + culture — may identify organism
- Rusty (blood-tinged) sputum: pneumococcal pneumonia
- Blood-streaked mucoid sputum: Mycoplasma, Streptococcal
- Validity limited by oropharyngeal contamination
Serology — Atypical Pneumonia
| Test | Organism | Notes |
|---|---|---|
| IgM by ELISA | Mycoplasma pneumoniae | Elevated during acute stage |
| IgG antibodies | Mycoplasma pneumoniae | Present after 1 week |
| Cold agglutinins | Mycoplasma | Elevated in 30–60% cases; non-specific |
| PCR (pharynx/sputum) | Mycoplasma | Confirmatory test |
Antigen Detection
- Polysaccharide antigen in urine/blood (pneumococcal) — not specific for pneumonia as may be positive in throat colonization alone
- Rapid RSV test — nasopharyngeal aspirate; identifies RSV in bronchiolitis/viral pneumonia
Additional Tests in Selected Cases
| Test | Indication |
|---|---|
| Blood glucose, calcium | Sick neonates and infants |
| Pleural fluid analysis | Suspected empyema / parapneumonic effusion |
| Pleural fluid culture | Essential for organism identification in empyema |
| CBNAAT (GeneXpert) | If TB pneumonia suspected |
| Mantoux / TST | TB workup |
| Immunoglobulins | Recurrent pneumonia (hypogammaglobulinemia) |
| Sweat chloride test | Recurrent pneumonia (cystic fibrosis) |
| HIV serology | If Pneumocystis or recurrent infections |
Pulse Oximetry
- Essential in all hospitalized children with pneumonia
- SpO₂ <92% in room air = significant hypoxemia → oxygen therapy required
- Continuous monitoring in severe disease
Summary: Minimum Workup for Hospitalized Pediatric Pneumonia
- CXR (PA / AP)
- CBC with differential
- Blood culture (before antibiotics)
- CRP / Procalcitonin
- Pulse oximetry
- Blood glucose (neonates / young infants)