Pneumonia diagnostic algorithm

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Alejandro Lemor, M.D. [2]

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Diagnostic Algorithm

Shown below is an algorithm for the diagnostic approach of pneumonia.
Abbreviations: HCAP: Healthcare-associated pneumonia; CAP: Community-acquired pneumonia; VAP: Ventilator-associated pneumonia; HAP: Hospital-acquired pneumonia; AMT: Abbreviated mental test score

Symptoms that suggest a lower respiratory tract infection: ❑ Fever ❑ Cough with sputum ❑ Dyspnea ❑ Pleuritic chest pain

Physical Examination Findings: ❑ Fever ❑ Tachypnea ❑ Tachycardia ❑ Dullness to percussion ❑ Bronchial breath sounds ❑ Rales ❑ Increased vocal fremitus ❑ Pleural friction rub

Order Labs: ❑ Complete blood count (CBC) ❑ Blood urea nitrogen (BUN) ❑ Sputum gram stain and culture ❑ Blood culture and ABG if necessary If atypical pneumonia is suspected, obtain: ❑ Urine legionella antigen, rapid influenza test ❑ Enyzme Immunoassay ❑ Immunofluorescence ❑ Polymerase chain reaction (PCR) for atypical and viral including influenza

❑ Order a chest X-ray if the patient presents with any of the following: Fever (>37.8° C / 100° F) Tachypnea (> 20 breaths/min) Tachycardia (> 100 bpm) Decreased breath sounds and crackles in the physical exam

Does the patient meets any of the following criteria for HCAP? Hospitalized in an acute care hospital for 2 or more days within 90 days of the infection; Resided in a nursing home or long-term care facility; Received recent intravenous antibiotic therapy, chemotherapy, or wound care within the past 30 days of the current infection; Attended a hospital or hemodialysis clinic

YES

NO The patient has CAP

Does the infection occurred ≥48 hours after admission and it was not present at admission?

Does the patient has at least 2 of the following CURB65 criteria? Confusion (AMT ≤8) Urea greater than 7 mmol/l (BUN > 20) Respiratory rate ≥ 30 breaths/min Blood pressure ≤ 90 systolic or ≤ 60 diastolic Age 65 or older

YES If the patient had an endotracheal tube placed ≥48 hours ago, suspect VAP. Otherwise, the patient has HAP

NO The patient has HCAP

YES Admit the patient and administer empiric inpatient antibiotic regimen

NO Administer empiric outpatient antibiotic regimen

Start empiric antibiotic therapy

CURB-65 Clinical Prediction Rule

CURB-65 is a clinical prediction rule that has been validated for predicting mortality in community-acquired pneumonia and infection of any site. The CURB-65 is based on the earlier CURB score and is recommended by the British Thoracic Society for the assessment of severity of pneumonia.

Calculation of CURB-65

The score is an acronym for each of the risk factors measured. Each risk factor scores one point, for a maximum score of 5:

Criteria	Score
Confusion (defined as an AMT of 8 or less)	1
Urea greater than 7 mmol/l (Blood Urea Nitrogen > 20)	1
Respiratory rate of 30 breaths per minute or greater	1
Blood pressure less than 90 systolic or diastolic blood pressure 60 or less	1
Age 65 or older	1

Interpretation of CURB-65: Risk of Death from Pneumnoia

The risk of death increases as the score increases.

CURB-65 Score	Risk of death
0	0.7%
1	3.2%
2	13.0%
3	17.0%
4	41.5%
5	57.0%

The CURB-65 has been compared to the pneumonia severity index in predicting mortality from pneumonia.

Interpretation of CURB-65: Risk of Death from any Infection

A cohort study of patients with any type of infection (half of the patients had pneumonia), the risk of death increases as the score increases:

• 0 to 1 <5% mortality
• 2 to 3 < 10% mortality
• 4 to 5 15-30% mortality

Infectious Diseases Society of America/American Thoracic Society Consensus Recommendation Criteria for Severe Community Acquired Pneumonia in Adults

The IDSA criteria are used to asses if a patient with community-acquired pneumonia requires ICU admission. Patients with at least one major criteria or ≥ 2 minor criteria should be admitted to the ICU.

Major Criteria

• Invasive mechanical ventilation
• Septic shock with the need for vasopressors

Minor Criteria

• Respiratory rate >30 breaths/min
• PaO2/FiO2 ratio <250
• Multilobar infiltrates
• Confusion/disorientation
• Uremia (BUN >20 mg/dL)
• Leukopenia (WBC <4000 cells/mm3)
• Thrombocytopenia (platelets < 100,000 cells/mm3)
• Hypothermia (temperature <36 degrees C)
• Hypotension that requires aggressive fluid resuscitation

Clinical Prediction Rule for Predicting Pulmonary Infiltrates Based on Clinical Findings

A clinical prediction rule found the five following signs from the medical history and physical examination best predicted infiltrates on the chest radiograph of 1134 patients presenting to an emergency room:

• Temperature > 100 degrees F (37.8 degrees C)
• Pulse > 100 beats/min
• Crackles
• Decreased breath sounds
• Absence of asthma

Probability of an Infiltrate
Based on the Number of Findings

Number of Findings	Primary Care	Emergency Room
5	47%	75%
4	27	56
3	8	22
2	4	11
1	1	3
0	1	2