II. Definitions

  1. Community Acquired Pneumonia (CAP)
    1. Lower respiratory tract infection
    2. Develops in non-hospitalized patient
    3. May be Bacterial, viral, fungal or parasitic
    4. May be present despite normal Chest XRay

III. Epidemiology: Community Acquired Pneumonia

  1. Incidence: 9.2 to 33 per 1000 person-years in U.S.
    1. All Adults: 248 cases per 100,000/year
    2. Adults 65 to 79 years: 634 cases per 100,000/year
    3. Adults >80 years: 16,430 cases per 100,000/year
  2. Most severe adult cases are in older adults over age 65 years
    1. Hospitalization rate 1,830 per 100,000/year in age over 65 years (contrast with 199 for under age 65 years)
  3. Adult mortality: 60,000 deaths per year from Pneumonia or Influenza (8th leading cause of death)
    1. Overall CAP Mortality 6% at 30 days (even with initial improvement)
    2. CAP Mortality 34% at 30 days for those who fail to initially improve or have unresolved Pneumonia
  4. U.S. cost/year for Community Acquired Pneumonia: $10-17 billion (90% of cost is inpatient care)

IV. Causes: Community Acquired Pneumonia

V. Risk Factors

  1. Age over 65 years
  2. Recent antibiotics
  3. Immune compromised (e.g. HIV Infection)
  4. Respiratory illness (COPD, Asthma)
  5. Vascular disease (CHF, CVA)
  6. Diabetes Mellitus
  7. Chronic Liver Disease
  8. Chronic Kidney Disease
  9. Cancer

VI. Findings: Signs and Symptoms

  1. Bacterial Pneumonia
    1. Cough
      1. Productive of Purulent Sputum with typical Bacteria
      2. Non-productive in atypical cases
    2. Sudden onset
    3. Fever and Chills
    4. Fatigue
    5. Ill appearing patient
    6. Pleuritic Chest Pain
    7. Dyspnea
    8. Tachypnea
    9. Tachycardia
  2. Viral Pneumonia
    1. Non-productive cough
    2. Gradual Onset with prodrome (malaise and Headache)
    3. Chest XRay more impressive than exam
    4. Onset in fall or winter
    5. Wheezing more common in viral causes
    6. Low grade Temperature (<101.3 F)
  3. Mycoplasma pneumonia
    1. Constant, harsh, non-productive cough
    2. Wheezing may occur in Mycoplasma pneumonia
    3. Fever typically lasts longer than 3 days
    4. More common in age over 3 years
  4. Legionella
    1. Onset with myalgias and Headache
    2. Fever to 104 F for first few days
    3. Gastrointestinal symptoms predominate in up to 40%
    4. Cough is late onset, mild, often non-productive

VII. Signs

  1. General findings
    1. Measured Fever
      1. Positive Likelihood Ratio: 2.1
      2. Negative Likelihood Ratio: 0.71
    2. Ill appearing patient
    3. Dyspnea
    4. Tachypnea
    5. Tachycardia
    6. Hypoxia (check Oxygen Saturation)
  2. Localized findings at involved lung region
    1. Egophony
      1. Positive Likelihood Ratio: 8.6
      2. Negative Likelihood Ratio: 0.96
    2. Dullness to percussion
      1. Positive Likelihood Ratio: 4.3
      2. Negative Likelihood Ratio: 0.79
    3. Rales
    4. Diminished breath sounds
    5. Bronchial breath sounds
    6. Tactile fremitus
  3. References
    1. Metlay (1997) JAMA 278(17): 1440-5 [PubMed]

VIII. Diagnosis: General

  1. See Diehr Rule to Diagnose Pneumonia
  2. Normal Vital Signs and Lung Exam in primary care reduces likelihood of Pneumonia to <0.4%
    1. Criteria: Normal Body Temperature, Respiratory Rate, Heart Rate and Lung Exam
    2. Community Acquired Pneumonia Likelihood reduced to<0.4% if criteria met
    3. Marchello (2019) J Am Board Fam Med 32(2): 234-47 [PubMed]
  3. Findings with highest Test Sensitivity for Pneumonia
    1. Fever and chills
    2. Pleuritic Chest Pain
    3. Cough productive of mucopurulent Sputum
    4. Dyspnea
    5. Tachypnea (especially in over age 65 years)
  4. Findings with highest Specificity
    1. Asymmetric breath sounds
    2. Pleural rubs
    3. Egophony
    4. Increased tactile fremitus

IX. Diagnosis: IDSA Pneumonia Criteria

  1. Major Criteria
    1. Septic Shock and need for Vasopressors
    2. Respiratory Failure requiring Mechanical Ventilation
    3. Leukopenia (WBC <4000 cells/ul) without other known cause
      1. Fore example, not due to Chemotherapy or underlying condition
  2. Minor Criteria
    1. Respiratory Rate >30 breaths per minute
    2. PaO2/FIO2 Ratio <250
    3. Multilobar infiltrates
    4. Confusion or Disorientation
    5. Blood Urea Nitrogen or BUN > 20 mg/dl (Uremia)
    6. Thrombocytopenia (Platelet Count <1000,000 cells/ul)
    7. Hypothermia (core Temperature <36.8 C)
    8. Hypotension (requiring aggressive fluid Resuscitation)
  3. Interpretation
    1. Pneumonia diagnosis positive if 1 major criteria or 3 minor criteria

X. Labs

  1. General
    1. Consider specific testing based on risks
      1. See Pneumonia Causes (as well as indications below)
    2. Lab Indications
      1. Moderate or severe Community Acquired Pneumonia
      2. Patient with comorbid conditions
    3. Efficacy of Labs
      1. No value in non-severe Community Acquired Pneumonia
      2. Theerthakarai (2001) Chest 119:181-4 [PubMed]
  2. Sputum Gram Stain and Culture
    1. See Sputum Culture
    2. Adequacy
      1. Good quality sample: <25 epithelial cells/LPF and contains Neutrophils
    3. Indications (IDSA/ATA 2019)
      1. Severe Pneumonia including ICU Admission (consider endotracheal aspirate if intubated)
      2. High risk for MRSA or Pseudomonas aeruginosa infection
      3. Hospitalized and received parenteral antibiotics in the last 90 days
      4. Older guideline indications in which Gram Stain and culture may still be indicated
        1. Cavitary infiltrates (obtain specific fungal and Tuberculosis cultures)
    4. Efficacy
      1. Sputum has low diagnostic yield in Community Acquired Pneumonia
        1. Not recommended in outpatient Community Acquired Pneumonia
        2. Ewig (2002) Chest 121:1486-92 [PubMed]
  3. Blood Culture
    1. Indications (IDSA/ATA 2019)
      1. Severe Pneumonia including ICU Admission (highest yield in severe Pneumonia)
      2. High risk for MRSA or Pseudomonas aeruginosa infection
    2. Efficacy
      1. Low sensitivity: Positive in only 5-10% of cases
      2. Does not predict severity or outcome
    3. References
      1. Campbell (2003) Chest 123:1142-50 [PubMed]
  4. Specific Testing with reasonable efficacy
    1. Covid19 PCR
      1. From March 2020 to at least June 2022 is typically obtained on most U.S. hospital admissions
    2. Influenza
      1. Rapid Influenza Test (Influenza DFA)
      2. Obtain in all Community Acquired Pneumonia cases during Influenza season
        1. Treat positive Influenza cases regardless of duration (i.e. even if >48-72 hours)
    3. Legionella pneumophila
      1. Rapid PCR of Sputum (80% Test Sensitivity)
      2. Urinary Antigen
        1. Test Sensitivity 70-90% (for serogroup 1, responsible for >80% of cases)
        2. Test Specificity 99%
      3. Indications (Legionella UAT per IDSA/ATS 2019)
        1. Severe Community Acquired Pneumonia including Intensive Care unit admission
        2. High risk for Legionella infection (e.g. Legionella outbreak)
    4. Mycoplasma pneumoniae
      1. Rapid PCR of Sputum (>30% Test Sensitivity)
    5. Chlamydia Pneumonia
      1. Rapid PCR (>30% Test Sensitivity)
    6. Streptococcus Pneumoniae (Pneumococcus)
      1. Pneumococcal Urine Antigen Test (UAT)
        1. Test Sensitivity 60-80%
        2. Test Specificity >90%
      2. Indications (Pneumococcal UAT per IDSA/ATS 2007)
        1. Intensive Care unit admission
        2. Failed outpatient antibiotic therapy
        3. Active Alcohol Abuse
        4. Chronic severe liver disease
        5. Leukopenia
        6. Asplenia
        7. Pleural Effusion
    7. Methicillin Resistant Staphylococcus Aureus (MRSA) Nasal Swab
      1. Indications include recent hospitalization with use of parenteral antibiotics
      2. See Methicillin Resistant Staphylococcus Aureus (MRSA) for risk factors
    8. Pseudomonas microbiologic screening
      1. Indications include recent hospitalization with use of parenteral antibiotics
      2. See Ventilator-Associated Pneumonia
  5. Other Testing
    1. Low Procalcitonin does not exclude Pneumonia
      1. Antibiotics should not be witheld based on low Procalcitonin alone
      2. IDSA does not recommend the use of Procalcitonin in Community Acquired Pneumonia
      3. Montassier (2019) Ann Emerg Med 74(4): 580-91 [PubMed]
  6. Thoracentesis with fluid analysis
    1. Indicated for Pleural Effusion >5 cm
    2. Send for Gram Stain, aerobic and anaerobic culture
  7. Fungal and TB Culture
    1. Cavitary lesions
    2. Foreign travel or immigration
  8. References
    1. Mandell (2007) Clin Infect Dis 44:S27–72 [PubMed]

XI. Imaging: Chest XRay

  1. Precautions: Underlying malignancy
    1. Confirm infiltrate resolution at 6 weeks after management (especially in smokers, or those over age 50)
  2. Precautions: Low Test Sensitivity in Pneumonia (esp. in early presentation)
    1. Chest XRay Test Sensitivity 43% (Test Specificity 93%) for pulmonary opacities consistent with Pneumonia
      1. Compared with CT Chest as the gold standard
    2. False Negatives are more common in early presentation
      1. However, Pneumonia is a clinical diagnosis, and may be diagnosed despite negative Chest XRay
    3. Serial Chest XRays may be needed, or consider bedside Lung Ultrasound or CT
      1. Repeat XRay during hospital admission is not needed if patient is clinically improving on management
    4. Negative Chest XRay does not exclude Pneumonia in severe illness
      1. Positive in only 40% of acute pneumococcal Community Acquired Pneumonia (CAP)
      2. Treat empirically as Community Acquired Pneumonia if high suspicion despite negative XRay
  3. Indications: All cases of suspected Community Acquired Pneumonia
    1. Any patient with at least 1 of the following
      1. Temperature >100 F (37.8 C)
      2. Heart Rate >100 beats/min
      3. Respiratory Rate >20 breaths/min
    2. Any patient with at least 2 of the following
      1. Decreased breath sounds
      2. Rales or crackles
      3. No Asthma history to explain findings
    3. Other indications (not included in Ebell protocol)
      1. Hypoxemia
      2. Confusion
      3. Known structural lung disease
      4. Age > 60 years old
      5. Systemic illness signs
    4. Ebell (2007) Am Fam Physician 76(4): 560-2 [PubMed]
  4. Causes: False Positives - alternative causes of infiltrates
    1. Atelectasis
    2. Acute Respiratory Distress Syndrome (ARDS)
    3. Lung Neoplasm
    4. Diffuse Alveolar Hemorrhage (e.g. immune disorder)
    5. Pulmonary Embolism with Lung Infarction
    6. Right-sided endocarditis with septic emboli
    7. Tuberculosis
    8. Interstitial Lung Disease (e.g. acute Chlorine gas inhalation, Farmer's Lung)
  5. Causes: Pneumonia with effusion (and other non-infectious effusions)
    1. Pneumococcal Pneumonia (most common)
    2. Staphylococcal Pneumonia
    3. Haemophilus Influenzae Pneumonia
    4. Legionella
    5. Tuberculosis (especially consider in comorbid HIV Infection)
    6. Predominately left-sided effusions (e.g. Aortic Dissection, Esophageal Rupture)
    7. Predominately right-sided effusions (e.g. CHF, Pancreatitis, hepatitis)
  6. Causes: Lung Cavitary Lesions
    1. Lung Abscess caused by Anaerobic Bacteria (most common)
    2. Staphylococcal Pneumonia
    3. Pseudomonas Pneumonia
    4. Tuberculosis
  7. Interpretation
    1. Lobar infiltrate suggests typical Bacterial Community Acquired Pneumonia (CAP)
    2. Diffuse, bilateral infiltrates suggests atypical Community Acquired Pneumonia (CAP)
  8. References
    1. Swadron (2019) Pulmonary 1, CCME Emergency Board Review, accessed 5/29/2019

XII. Imaging: Advanced

  1. CT Chest
    1. CT Chest is considered gold standard and frequently identifies Pneumonia not seen on Chest XRay
    2. CT Chest identifies more than twice as my Pneumonia cases not visualized on Chest XRay
    3. CT Chest excludes Pneumonia in False Positive Pneumonia cases based on Chest XRay
    4. Self (2013) Am J Emerg Med 31(2): 401–405. [PubMed]
  2. Lung Ultrasound
    1. May be more accurate than Chest XRay in the diagnosis of Pneumonia
    2. Findings consistent with Pneumonia
      1. Localized B-Line artifacts (Interstitial Edema)
      2. Localized liver-like appearance of lung (consolidation)
    3. Also defines other respiratory conditions at the bedside (e.g. Pneumothorax, Pleural Effusion)
    4. Test Sensitivity: 94 to 95%
    5. Test Specificity: 90 to 96%
    6. Chavez (2014) Respir Res 15:50 [PubMed]
    7. Ye (2015) PLoS One 10(6): e0130066 [PubMed]

Images: Related links to external sites (from Bing)

Related Studies

Ontology: Pneumonia, Bacterial (C0004626)

Definition (MSH) Inflammation of the lung parenchyma that is caused by bacterial infections.
Definition (NCI) Acute infection of the lung parenchyma caused by bacteria (e.g., Streptococcus pneumoniae, Haemophilus influenzae, Chlamydia pneumoniae, Mycoplasma pneumoniae, and Legionella pneumophila). Signs and symptoms include productive cough, fever, chills, shortness of breath, and chest pain.
Definition (CSP) pneumonia caused by various species of bacteria; commonly results from bronchogenic spread of infection following microaspiration of secretions.
Concepts Disease or Syndrome (T047)
MSH D018410
ICD9 482.9
ICD10 J15.9
SnomedCT 195891009, 195892002, 155553007, 53084003
English Bacterial Pneumonia, Bacterial Pneumonias, Pneumonia, Bacterial, Pneumonias, Bacterial, Bacterial pneumonia, unspecified, Pneumonia due to bacteria NOS, BACT PNEUMONIA, PNEUMONIA BACT, bacterial pneumonia (diagnosis), bacterial pneumonia, Pneumonia bacterial NOS, Bacterial pneumonia NOS, Unspecified bacterial pneumonia, Pneumonia, Bacterial [Disease/Finding], Pneumonia;bacterial, pneumonia bacterial, Pneumonia due to bacteria NOS (disorder), Bacterial pneumonia NOS (disorder), Pneumonia bacterial, Bacterial pneumonia, Bacterial pneumonia (disorder), bacterial; pneumonia, pneumonia; bacterial, Bacterial pneumonia, NOS
Dutch bacteriële pneumonie NAO, bacteriële pneumonie, niet-gespecificeerd, bacterieel; pneumonie, pneumonie; bacterieel, Bacteriële pneumonie, niet gespecificeerd, bacteriële pneumonie, Bacteriële pneumonie, Pneumonie, bacteriële
French Pneumonie bactérienne non précisée, Pneumonie bactérienne SAI, Pneumonie bactérienne, Pneumopathie bactérienne
German Pneumonie bakteriell NNB, bakterielle Pneumonie, unspezifisch, Bakterielle Pneumonie, nicht naeher bezeichnet, Pneumonie durch Bakterien, Pneumonie, bakterielle
Italian Polmonite batterica NAS, Polmonite batterica, non specificata, Polmonite batterica
Portuguese Pneumonia bacteriana NE, Pneumonia bacteriana, Pneumonia Bacteriana
Spanish Neumonía bacteriana no especificada, Neumonía bacteriana NEOM, neumonía bacteriana, SAI, neumonía bacteriana, SAI (trastorno), neumonía debida a bacterias, SAI (trastorno), Bacterial pneumonia NOS, neumonía debida a bacterias, SAI, neumonía bacteriana (trastorno), neumonía bacteriana, neumonía bactérica, Neumonía bacteriana, Neumonía Bacteriana
Japanese 細菌性肺炎、詳細不明, 細菌性肺炎NOS, サイキンセイハイエンショウサイフメイ, サイキンセイハイエン, サイキンセイハイエンNOS, 肺炎-細菌性, 細菌性肺炎
Swedish Lunginflammation, bakteriell
Finnish Bakteeripneumonia
Czech Bakteriální pneumonie, Bakteriální pneumonie, blíže neurčená, Bakteriální pneumonie NOS, bakteriální pneumonie, pneumonie bakteriální
Korean 상세불명의 세균성 폐렴
Polish Zapalenie płuc bakteryjne
Hungarian bacterialis pneumonia, bacterialis pneumonia k.m.n., bacterialis tüdőgyulladás, nem meghatározott
Norwegian Bakteriell lungebetennelse, Lungebetennelse, bakteriell, Bakteriell pneumoni, Pneumoni, bakteriell

Ontology: Pneumonia (C0032285)

Definition (MSH) Inflammation of any part, segment or lobe, of the lung parenchyma.
Definition (MEDLINEPLUS)

Pneumonia is an infection in one or both of the lungs. Many germs, such as bacteria, viruses, and fungi, can cause pneumonia. You can also get pneumonia by inhaling a liquid or chemical. People most at risk are older than 65 or younger than 2 years of age, or already have health problems.

Symptoms of pneumonia vary from mild to severe. See your doctor promptly if you

  • Have a high fever
  • Have shaking chills
  • Have a cough with phlegm that doesn't improve or gets worse
  • Develop shortness of breath with normal daily activities
  • Have chest pain when you breathe or cough
  • Feel suddenly worse after a cold or the flu

Your doctor will use your medical history, a physical exam, and lab tests to diagnose pneumonia. Treatment depends on what kind you have. If bacteria are the cause, antibiotics should help. If you have viral pneumonia, your doctor may prescribe an antiviral medicine to treat it.

Preventing pneumonia is always better than treating it. Vaccines are available to prevent pneumococcal pneumonia and the flu. Other preventive measures include washing your hands frequently and not smoking.

NIH: National Heart, Lung, and Blood Institute

Definition (NCI_NCI-GLOSS) A severe inflammation of the lungs in which the alveoli (tiny air sacs) are filled with fluid. This may cause a decrease in the amount of oxygen that blood can absorb from air breathed into the lung. Pneumonia is usually caused by infection but may also be caused by radiation therapy, allergy, or irritation of lung tissue by inhaled substances. It may involve part or all of the lungs.
Definition (NCI) An acute, acute and chronic, or chronic inflammation focally or diffusely affecting the lung parenchyma, due to infections (viruses, fungi, mycoplasma, or bacteria), treatment (e.g. radiation), or exposure (inhalation) to chemicals. Symptoms include cough, shortness of breath, fevers, chills, chest pain, headache, sweating, and weakness.
Definition (CSP) inflammation of the lungs with consolidation and exudation.
Concepts Disease or Syndrome (T047)
MSH D011014
ICD10 J18.9
SnomedCT 274103002, 155552002, 155558003, 266391003, 155548002, 60363000, 205237003, 233604007
LNC LP21407-9, MTHU020831, LA7465-3
English Pneumonitis, Pneumonia, Pneumonias, Pneumonia, unspecified, Pneumonitides, Pneumonia NOS, pneumonia (diagnosis), pneumonia, Pneumonitis NOS, Pneumonia [Disease/Finding], Pneumoniae, inflammation lungs, unspecified pneumonia, pneum, pulmonary inflammation, lung inflammation, Inflammation, Lung, Inflammation, Pulmonary, Inflammations, Lung, Inflammations, Pulmonary, Lung Inflammation, Lung Inflammations, Pulmonary Inflammation, Pulmonary Inflammations, Pneumonia NOS (disorder), Pulmonary inflammation, Lung inflamed, Pulmonitis, PNEUMONIA, Pneumonia (disorder), Pneumonia, NOS, Pneumonia (disorder) [Ambiguous], pneumonitis
French PNEUMONIE, Congestion pulmonaire SAI, Pneumonite, Pneumonie SAI, Pneumopathie infectieuse, Pneumonie
Portuguese PNEUMONIA, Pneumonite NE, Pulmonite, Pneumonia NE, Pulmonia, Pneumonia, Inflamação do Pulmão, Inflamação Pulmonar, Pneumonite
Spanish NEUMONIA, Neumonitis NEOM, Neumonía NEOM, neumonia, SAI (trastorno), Pneumonia NOS, neumonia, SAI, Pneumonía, Pulmonía, neumonía (concepto no activo), neumonía (trastorno), neumonía, Neumonitis, Inflamación del Pulmón, Inflamación Pulmonar, Neumonía
German PNEUMONIE, Pneumonie NNB, Pulmonitis, Pneumonitis NNB, Pneumonie, nicht naeher bezeichnet, Lungenentzuendung, Pneumonie, Pneumonitis, Lungenentzündung
Italian Infezione polmonare, Polmonite aspecifica, Infezione dei polmoni, Infezione polmonare aspecifica, Pneumonite, Infiammazione del polmone, Infiammazione polmonare, Polmonite
Dutch pneumonie NAO, pneumonitis NAO, pulmonitis, Pneumonie, niet gespecificeerd, pneumonie, Pneumonie, Longontsteking, Pneumonitis
Japanese 肺炎NOS, 肺臓炎, 肺臓炎NOS, ハイエンNOS, ハイエン, ハイゾウエンNOS, ハイゾウエン, 肺炎
Swedish Lunginflammation
Czech pneumonie, Pneumonie, Pulmonitida, Pneumonie NOS, Pneumonitida NOS, zápal plic, zánět plic
Finnish Keuhkokuume
Korean 상세불명의 폐렴
Polish Zapalenie płuc
Hungarian pneumonia, Pneumonitis k.m.n., pneumonia k.m.n., Pulmonitis
Norwegian Pneumoni, Lungebetennelse

Ontology: Community acquired pneumonia (C0694549)

Concepts Disease or Syndrome (T047)
SnomedCT 385093006
Dutch community-acquired pneumonie
French Pneumonie communautaire
German Community acquired Pneumonie (CAP)
Italian Polmonite comunitaria
Portuguese Pneumonia adquirida na comunidade
Spanish Neumonía adquirida en la comunidad, neumonía adquirida en la comunidad, neumonía extrahospitalaria (trastorno), neumonía extrahospitalaria
Japanese 市中感染性肺炎, シチュウカンセンセイハイエン
English community-acquired pneumonia, community-acquired pneumonia (diagnosis), community acquired pneumonia, acquired community pneumonia, Community acquired pneumonia, Community acquired pneumonia (disorder)
Czech Komunitní pneumonie
Hungarian Közösségben szerzett pneumonia

Ontology: Atypical pneumonia (C1412002)

Concepts Disease or Syndrome (T047)
SnomedCT 195932001, 233606009, 35037009
English Atypical pneumonia, Pneumonia;atypical, atypical pneumonia (diagnosis), Atypical pneumonia (disorder), atypical; pneumonia, pneumonia; atypical, atypical pneumonia
Czech Atypická pneumonie
Dutch atypische pneumonie, atypisch; pneumonie, pneumonie; atypisch
French Pneumonie atypique
German atypische Pneumonie
Hungarian atípusos pneumonia
Italian Polmonite atipica
Japanese イケイハイエン, 異型肺炎
Portuguese Pneumonia atípica
Spanish Neumonía atípica, neumonía atípica (trastorno), neumonía atípica