Community Acquired Pneumonia (CAP) in Adults

Question 1

Background

Answer 1

• CAP can be difficult to diagnose and has a significant mortality in some patients, particularly older Māori.
• In general, clinicians are poor at risk‑stratifying patients, so tend to under-treat severe CAP (with high mortality risk) and over-treat mild CAP (with low mortality risk).
• An important decision for GPs is whether to manage in the community or admit acutely, depending on the assessment of severity, co-morbidities, and social circumstances. The CRB-65 severity assessment tool assists with this decision.
• Streptococcus pneumoniae is the leading cause of CAP, requiring early and appropriate antibiotics in sufficient dosage. Low doses of penicillin-based antibiotics are a common cause of poor patient outcomes.
• Pneumonia caused by Legionella:
• This is much more common than previously thought, is probably under-recognised, and is responsible for many of the most severe cases of CAP.
• Person-to-person transmission of Legionella has not been demonstrated.

Question 2

Aetiology and epidemiology

Answer 2

No organism is identified in over 40% of cases.

Multiple organisms are identified in 15% of cases.

A causative organism cannot be accurately predicted from clinical features.

Aetiology and clinical features:

1) Streptococcus pneumoniae:
* Most commonly identified, especially in winter and overcrowded settings.
* Increasing age.
* Co‑morbidities, i.e. diabetes, COPD, alcohol abuse.
* Acute onset.
* High fever, pleuritic pain.

2) Haemophilus influenzae:
* COPD.
* Aged > 65 years.

3) Mycoplasma pneumoniae:
* More common in epidemics, which may occur every 4 years.
* Younger age.
* Prior antibiotics.
* Less multi-system involvement.

4) Staphylococcus aureus:
* Uncommon (more common in winter).
* Causes severe illness with a high mortality.
* May follow soon after an episode of influenza.

Question 3

Legionella

Answer 3

Risk factors:
* Gardening – recent history of using potting mix or compost, tipping or trowelling of potting mix, or hand‑to‑face touching (eating, drinking, or smoking) before hand washing.
* Water – exposure to potentially contaminated water sources, such as humidifiers, air conditioners, or hot water systems.

Much more common during the spring and summer months.

Symptoms are less helpful than risk factors in assessing risk for Legionella, but may include:
* dry coughing.
* high fever, chills.
* shortness of breath, chest pains.
* headaches, excessive sweating, nausea, vomiting.
* abdominal pain.
* diarrhoea, which is more common than with other forms of community-acquired pneumonia.

Question 4

Uncommon pathogens:

Answer 4

1) Gram‑negative enteric bacilli.

2) Legionella pneumophila – Exposure to potting mix or contaminated water sources, e.g. air conditioning units.

3) Chlamydia psittaci – Rare, associated with farmed or pet birds.

4) Pneumocystis jiroveci – Severe immunosuppression, e.g. untreated HIV infection, organ transplantation, and long‑term cortico‑steroid treatment.

5) Mycobacterium tuberculosis – Needs to be considered where relevant, e.g:
* immigrants from high incidence countries, e.g. India, China, South Korea, South Africa.
* overseas travel, ethnicity, social deprivation, elderly.
* clinical features, e.g. persistent cough, haemoptysis, malaise, weight loss, and night sweats.

6) Aspiration is a risk factor in the elderly (especially in residential care facilities):
* 10% have coincidental S. aureus.
* Usually multiple organisms including anaerobes.

NB: Pneumococcal, staphylococcal, and Legionella infection tend to cause more severe illness, and are associated with the highest mortality rates.

Question 5

Risk factors for CAP

Answer 5

• Low socio-economic status
• Poor nutrition
• Poor housing quality including chronic exposure to damp, mould, and overcrowding
• Exposure to tobacco smoke
• Māori and Pacific peoples have a higher incidence than other ethnic groups.

Question 6

About pneumonia in Māori:

Answer 6

• Māori men with CAP aged 50 to 64 years have 3.5 times more hospitalisations than non-Māori men, with a 6 times higher mortality rate than non-Māori.
• Māori women with CAP aged over 65 years have 3 times more hospitalisations than non-Māori women, with no difference in mortality.
• Māori, particularly children and older adults, are more likely to have socio-economic factors which increase CAP incidence and severity.
• For communication, needs, and preferences for Māori patients, see Hauora Māori (Māori Health) Competency.

Question 7

Assessment
Practice point

Answer 7

• Ask the patient if they have used potting mix or compost in the last 2 weeks.
• and if they have, give antibiotics for Legionella.

Question 8

Alternative diagnoses

Answer 8

• Acute bronchitis with or without underlying lung pathology, e.g. COPD
• Heart failure
• Pulmonary embolism (PE)
• Aspiration pneumonitis
• Travel-acquired respiratory infections
• Pneumothorax
• Acute intra-abdominal pathologies, e.g. pyelonephritis, acute cholecystitis, and acute pancreatitis can mimic CAP.
• Tuberculosis

Question 9

History:

Answer 9

• Ask about symptoms of an acute lower respiratory tract illness, i.e. cough and at least one other lower respiratory tract symptom, e.g. dyspnoea, sputum, or pleuritic chest pain.
• Assess for risk factors for CAP.
• Always consider Legionella as a causative agent.

Question 10

Examination:

Answer 10

Measure respiratory rate, temperature, heart rate, blood pressure, and oxygen saturation (SaO2).

Examine the chest for quality of breath entry, presence of wheeze, and signs of pneumonia.

Suspect CAP if clinical features of pneumonia are present. Check for:
* symptoms of an acute lower respiratory tract illness, i.e. cough and at least one other lower respiratory tract symptom, e.g. increased dyspnoea, increased sputum, or pleuritic chest pain.
* evidence of systemic illness – temperature above 38°C and/or sweating, fevers, shivers, aches, and pains.
* new focal chest signs on examination.
* no other explanation for the illness.

Clinical chest signs are variable, ranging from clear signs of consolidation to no focal signs at all.

Immunosuppressed and elderly patients more frequently present with non-specific symptoms, and may not have a fever.

Question 11

Calculate the CRB-65 severity score

Answer 11

Take into account clinician gut feeling to help determine antibiotic choice, and suitability for community management.

CRB-65 severity score:
Score 1 point for each feature present:

1. Confusion – use an abbreviated mental test.
2. Respiratory rate 30 or more breaths per minute.
3. Blood pressure:
   * Systolic blood pressure less than 90 mmHg, or
   * Diastolic blood pressure 60 mmHg or less.
4. 65 years or older.

Question 12

Abbreviated mental test

Answer 12

Each question below scores 1 mark. A score of 8 or less has been used to define mental confusion in the CRB-65 severity score. Ask about:

• age
• recognition of two persons, e.g. doctor, nurse
• date of birth
• recalling address, e.g. 42 West Street
• time to the nearest hour
• date of the second world war
• year
• name of prime minister
• address or location (ask the patient where they are)
• counting backwards 20 to 1

Question 13

CRB-65 Severity Score
Consider social circumstances and home support when deciding on whether to refer to hospital or manage in the community.

Answer 13

Question 14

Suitability for community management

Answer 14

If the CRB-65 score is 0, determine suitability for community management – consider:

• the patient’s ability to access, tolerate, and reliably take medication.
• if the patient has adequate social support and phone access.
• if the patient wishes to and has the ability to cope at home.
• your ability to monitor the patient safely.
• features suggesting complications of pneumonia, e.g. empyema, lung abscess, septicaemia.
• other co-morbidities:
• Frailty, e.g. the patient is bedridden or in residential care
• Diabetes
• Ischaemic heart disease (IHD)
• Obesity
• Chronic lung or liver disease
• Alcohol abuse
• Immunosuppression, e.g. cancer, post‑splenectomy, HIV