Study characteristics
| Study | Location | Age range | Inclusion and exclusion criteria | Sample size | Radiographic pneumonia, N (%) | Definition of pneumonia by chest radiograph |
| Puumalainen et al and Arcay, et al. (ARIVAC)48 49 | Philippines | 6 weeks to 59 months | Tachypnoea*, lower chest indrawing (severe pneumonia)† or cyanosis and/or inability to drink (very severe pneumonia)‡ | 1153 | 187 (16.2) | Primary end point pneumonia (PEP)§ |
| Basnet et al50 | Nepal | 2–35 months | Cough <14 days and/or difficulty breathing ≤72 hours with presence of lower chest indrawing, provided lower chest indrawing persisted after 3 doses of bronchodilators. | 551 | 135 (24.5) | Lobar pneumonia/ consolidation¶ |
| Gentile et al51 | Argentina | 0–59 months | Children hospitalised with pneumonia. | 401 | 201 (50.1) | PEP§ |
| Gessner et al52 | Indonesia | 0–24 months | WHO defined non-severe** and severe pneumonia†. | 5814 | 1025 (17.6) | PEP§ |
| Hortal et al53 | Uruguay | 0–59 months | Children hospitalised with acute lower respiratory tract infection with chest X-ray performed. | 811 | 412 (50.8) | PEP§ |
| Tan et al54 | Indonesia | <5 years | All children with diagnosis of pneumonia and having >1 of the following: fever, cough, dyspnoea, or tachypnoea*. | 1251 | 128 (10.2) | Lobar pneumonia/ consolidation¶ |
| Neuman, et al24 | USA | 0–59 months | Children with chest X-ray performed for suspicion of pneumonia. Excluded children with chronic conditions. | 1796 | 161 (9.0) | PEP§ |
| O'Grady et al55 | Central Australia | 0–59 months | Child with cough with tachypnoea* and/or chest indrawing†. Excluded children with wheezing and chronic conditions. | 147 | 40 (27.2) | PEP§ |
| Ferrero et al56 | Argentina | 1–59 months | WHO defined non-severe** and severe pneumonia†. Excluded hospital-acquired pneumonia. | 2085 | 1123 (53.9) | PEP§ |
| Turner et al57 | Thailand | 0–2 years | WHO defined non-severe** and severe pneumonia†. | 1020 | 331 (32.5) | PEP§ |
*Tachypnoea: respiratory rate ≥60 per minute in infants <2 months old, ≥50 per minute in infants 2–11 months old, or ≥40 per minute in children 12–59 months of age.
†Severe pneumonia (old WHO pneumonia classification): cough and/or fast breathing with lower chest indrawing.
‡Very severe pneumonia (old WHO pneumonia classification): one or more danger sign including abnormally sleepy, lethargy, central cyanosis, inability to drink, convulsions, head nodding/bobbing, nasal flaring or grunting.
§PEP: a dense opacity that may be a fluffy consolidation of a portion or whole of a lobe or of the entire lung, often containing air bronchograms and sometimes associated with pleural effusion.
¶Lobar pneumonia or consolidation: Chest X-ray findings showing lobar pneumonia or consolidation.
**Non-severe pneumonia: cough and fast breathing, defined as respiratory rate of >50 per minute in children 2–11 months old or >40 per minute in children 12–59 months old.