Table 3 ▪.

Influence on Test Characteristics Using Different Sets of Chief Complaints as Preselection Criteria

	Patients with Pneumonia Included (%)	Pneumonia Prevalence (%)	Positive Predictive Value (%)	Negative Predictive Value (%)	Specificity (%)
Most frequent chief complaint	55	10.4	15.5	98.8	44.4
Three most frequent chief complaints	80	6.2	14.8	99.6	67.6
Eight most frequent chief complaints	91	2.9	13.1	99.8	83.1
All chief complaints	100	1.7	13.1	99.9	90.7

Note: Depending on which chief complaints were included in the four different sets, the number of included patients with and without pneumonia varied. For each set, the sensitivity level was set at 95% and the respective test characteristics computed.