History and exam

Key diagnostic factors

common

cough with increasing sputum production

Usually present. Less common in older patients.

fever or chills

Usually present. Less common in older patients.

dyspnea

Usually present.

pleuritic pain

Associated with bacteremia in outpatients.

abnormal auscultatory findings

Asymmetric breath sounds, pleural rubs, egophony (increased resonance of voice sounds heard on auscultation), and increased fremitus may be heard.

Pleural rubPleural rub

Other diagnostic factors

common

dullness to percussion

Suggests consolidations and/or pleural effusion.

myalgia

Nonspecific symptom that is often reported.

arthralgia

Nonspecific symptom that is often reported.

uncommon

confusion

Not generally common but often seen in older patients.

Risk factors

strong

age >65 years

Incidence increases significantly with age. Very advanced age has been associated with higher mortality from CAP.[37]

residence in a healthcare setting

Approximately 10% to 18% of all patients hospitalized for pneumonia are nursing home residents. Mortality in these patients may reach 55%.[38][39] Patients in residential homes who develop pneumonia have traditionally been considered to have healthcare-associated pneumonia (HCAP) and not CAP. However, this definition has been criticized because it is not able to distinguish patients at risk for resistant pathogens, and each patient ought to be evaluated individually.

COPD

Associated with a 2- to 4-fold increased risk of CAP.[32] Data from one study conducted in patients with CAP compared the outcome of patients with and without COPD and found that the presence of COPD was an independent risk factor for mortality.[40]

exposure to cigarette smoke

Colonization with pathogenic bacteria is frequent in smokers and presents an increased risk of lung infections, especially pneumococcal pneumonia.[41] One study of bacterial pneumonia found that HIV-infected smokers had >80% higher risk of developing pneumonia than those who had never smoked.[42][43] Another study showed that current smokers with pneumococcal CAP often develop sepsis and require hospitalization at a younger age despite having fewer comorbid conditions than older patients.[44] Current and former smokers are more likely to develop CAP than never-smokers.[45] Passive smoking at home is a risk factor for CAP in people aged 65 years or older.[45][46]

alcohol abuse

There is clear evidence that alcohol consumption increases the risk for CAP. A meta-analysis of 14 studies found that people who consumed alcohol at all or in higher amounts had an 83% higher risk of CAP compared to people who consumed no alcohol or lower amounts (relative risk of 1.83).[47] Consumption of 24 g, 60 g, and 120 g of pure alcohol daily has been shown to result in a relative risk for incident CAP of 1.12 (95% CI, 1.02 to 1.23), 1.33 (95% CI, 1.06 to 1.67), and 1.76 (95% CI, 1.13 to 2.77), respectively, relative to nondrinkers.[48]

poor oral hygiene

Oral and respiratory bacteria in dental plaques are shed into the saliva and can then be aspirated into the lower respiratory tract to cause infection. Aspiration pneumonia is one of the most serious problems in older patients. Low-quality evidence suggests that professional oral health care measures (e.g., brushing, swabbing, denture cleaning, mouth rinses) may reduce mortality due to pneumonia in nursing home residents compared to usual care. However, the effect of these measures on preventing pneumonia remains unclear.[49]

use of acid-reducing drugs, inhaled corticosteroids, antipsychotics, antidiabetic drugs

CAP is one of the most common adverse effects associated with use of proton-pump inhibitors.[50] This is thought to be due to a decrease in gastric acid secretion, which allows pathogens to colonize the upper respiratory tract more easily. Outpatient use of these drugs is associated with a 1.5-fold increased risk of CAP.[51] H2 receptor antagonists may also be associated with an increased risk of CAP.[52]

Other drugs that have been independently associated with an increased risk for CAP include inhaled corticosteroids (especially at higher doses), antipsychotics (especially atypical antipsychotics and in older people), and antidiabetic medications.[53]

contact with children

Regular contact with children is associated with an increased risk of CAP.[54] Two studies have reported that having children in the household increases the adjusted odds ratio from 1.00 for households with no children to 3.2,[55] or 3.41[56] for households with 3 or more children.

HIV infection

Patients with HIV infection are more susceptible to bacterial CAP. Although antiretroviral therapy has improved the immune response and reduced the incidence of CAP, it remains a major cause of morbidity and mortality in these patients, in part because they show altered immunity and because immune activation persists. Mortality in HIV-infected patients with CAP ranges from 6% to 15%.[57]

weak

diabetes mellitus

Associated with a moderate increase in the risk of CAP. The main reasons are the increased risk of aspiration, hyperglycemia, decreased immunity and impaired lung function, and coexisting morbidity.

One study found that diabetes (type 1 and type 2) was a risk factor for pneumonia-linked hospitalization. Another study[58] reported that pre-existing diabetes was associated with a higher risk of death after hospitalization for CAP compared with patients hospitalized for noninfectious illnesses.[59] The risk of severe pneumococcal bacteremia is also higher in diabetic patients.[60]

chronic renal disease

A significant risk factor for mortality in patients with CAP.[61][62]

chronic liver disease

It is known that bacterial infections occur in 32% to 34% of hospitalized patients with cirrhosis, and approximately 15% of these infections are pneumonia (the third most common cause of infection in these patients).[63] One study reported that chronic liver disease is a risk factor for pulmonary complications in patients hospitalized with pneumococcal pneumonia.[64]

use of opioids

A case-control study found that prescribed opioids, especially those with immunosuppressive properties or higher doses, are associated with an increased risk of CAP in people with and without HIV infection.[65]

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