The inclusion criteria included a mix of ARI symptoms and abnormal vital signs or physical examination findings. All patients received a chest radiograph and a CT within 4 hours of presentation. Chest radiographs identified opacities consistent with PNA in 188 of 319 (59%) patients. CT revealed PNA in 40 (33%) of the 131 patients without opacity on chest radiographs and excluded PNA in 56 (29.8%) of the 188 patients with opacities on chest radiographs. Because of CT, antibiotics were initiated in 51 (16%) patients and discontinued in 29 (9%) patients. CT findings also resulted in 22 additional hospitalizations and 23 discharges. The available data clearly show that CT is more accurate than chest radiographs for the diagnosis of PNA. In most cases a combination of vital signs and physical examination findings, along with judicious use of chest radiographs, is deemed sufficient for diagnosing or excluding PNA. However, in certain patients, such as those who cannot reliably follow-up or for whom any delay in diagnosis of PNA could be life-threatening (such as patients with advanced age, unreliable follow-up, or significant comorbidities), chest CT may be warranted when initial chest radiograph is negative or equivocal [24,32,34]. The IDSA/ATS consensus guidelines consider CT a reasonable alternative to empiric antibiotic therapy with follow-up chest radiographs when there is a high clinical suspicion of PNA [4]. Given the difficulty of obtaining an accurate history and physical examination and the high incidence of PNA in patients with organic brain disease, CT is a reasonable alternative to empiric treatment antibiotics in the setting of a negative or equivocal initial chest radiograph. US Chest Studies performed by Reissig et al [11] and Bourcier et al [8] suggest that US has a higher sensitivity than radiographs for PNA, implying that US may add value in cases in which PNA is suspected but initial chest radiographs are negative or equivocal.
Acute Respiratory Illness in Immunocompetent Patients. The inclusion criteria included a mix of ARI symptoms and abnormal vital signs or physical examination findings. All patients received a chest radiograph and a CT within 4 hours of presentation. Chest radiographs identified opacities consistent with PNA in 188 of 319 (59%) patients. CT revealed PNA in 40 (33%) of the 131 patients without opacity on chest radiographs and excluded PNA in 56 (29.8%) of the 188 patients with opacities on chest radiographs. Because of CT, antibiotics were initiated in 51 (16%) patients and discontinued in 29 (9%) patients. CT findings also resulted in 22 additional hospitalizations and 23 discharges. The available data clearly show that CT is more accurate than chest radiographs for the diagnosis of PNA. In most cases a combination of vital signs and physical examination findings, along with judicious use of chest radiographs, is deemed sufficient for diagnosing or excluding PNA. However, in certain patients, such as those who cannot reliably follow-up or for whom any delay in diagnosis of PNA could be life-threatening (such as patients with advanced age, unreliable follow-up, or significant comorbidities), chest CT may be warranted when initial chest radiograph is negative or equivocal [24,32,34]. The IDSA/ATS consensus guidelines consider CT a reasonable alternative to empiric antibiotic therapy with follow-up chest radiographs when there is a high clinical suspicion of PNA [4]. Given the difficulty of obtaining an accurate history and physical examination and the high incidence of PNA in patients with organic brain disease, CT is a reasonable alternative to empiric treatment antibiotics in the setting of a negative or equivocal initial chest radiograph. US Chest Studies performed by Reissig et al [11] and Bourcier et al [8] suggest that US has a higher sensitivity than radiographs for PNA, implying that US may add value in cases in which PNA is suspected but initial chest radiographs are negative or equivocal.