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Make the Diagnosis: Does This Child Have Pneumonia?

Prior Probability of Pneumonia in Children With Respiratory Symptoms

The majority of children in studies of childhood pneumonia are ≤ 5 y of age. The probability of childhood pneumonia varies by geography. Studies of the diagnostic accuracy of pneumonia usually include a predominance of younger children who are brought to acute care settings because their parents are concerned by the severity of their respiratory illness and associated symptoms. In US and Canadian studies, among such children, the prevalence of radiographically defined pneumonia is 19% (95% CI, 11%-31%). In studies done outside North America, the prevalence is 37% (95% CI, 26%-50%).

Population Among Whom Childhood Pneumonia Should Be Considered

Pneumonia is considered part of the differential diagnosis in children who present to outpatient clinics, emergency departments, or inpatient units with respiratory symptoms. In studies of the clinical examination, 80% of the children had cough along with a parental report of fever. Other findings such as poor feeding in the youngest children, nausea, vomiting, difficulty breathing, or tachypnea have high variability in their frequency across studies. Thus, children brought in for evaluation of cough and fever are the primary representative group for whom pneumonia should be considered. In other children, a variety of symptoms and signs might suggest pneumonia.

Assessing the Likelihood That a Child Has Pneumonia

There are many reasons that children may have a cough, so it is not surprising that the presence of a cough alone is not useful for identifying children with pneumonia (see Table 103-1). However, the absence of a cough is associated with a reduced likelihood of pneumonia (LR, 0.47; 95% CI, 0.24-0.70). Among adolescents, the presence of chest discomfort is associated with increased likelihood of pneumonia (LR range, 1.5-5.5).

Table 103-1.Useful Findings for Identifying Children With Pneumonia

The most useful vital sign finding is oxygen saturation. Children with normal oxygen saturation (> 96%) are less likely to have pneumonia (LR, 0.47; 95% CI, 0.32-0.67), compared with those with hypoxemia (LR, 2.8; 95% CI, 2.1-3.6). However, the strength of the association is not consistent among those with hypoxemia. Children with the lowest saturations (< 90%) have a statistically lower LR (LR, 1.5; 95% CI, 1.1-1.9), which suggests that causes other than pneumonia should be considered in these most hypoxemic children. No temperature threshold ...

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