High-Yield ATS/IDSA 2019 CAP guidelines

Pneumonia

ATS/IDSA CAP — Core Principles

CAP guideline year and societies
→ 2019 ATS/IDSA

CAP definition used in guideline
→ Pneumonia acquired outside the hospital with radiographic confirmation

Patients excluded from guideline
→ Immunocompromised adults (HIV with low CD4, chemo, transplant)

Diagnostic Testing

Routine sputum Gram stain/culture in outpatient CAP
→ Not recommended

Routine blood cultures in outpatient CAP
→ Not recommended

Indications for sputum culture in hospitalized CAP
→ Severe CAP OR MRSA/Pseudomonas risk factors OR recent hospitalization with IV antibiotics

Indications for blood cultures in hospitalized CAP
→ Severe CAP OR MRSA/Pseudomonas risk factors OR recent hospitalization with IV antibiotics

Most consistent risk factor for MRSA or Pseudomonas
→ Prior respiratory isolation of the organism

Urinary Antigen Testing

Routine pneumococcal urine antigen testing
→ Not recommended

When to test for pneumococcal urine antigen
→ Severe CAP

Routine Legionella urine antigen testing
→ Not recommended

Indications for Legionella testing
→ Severe CAP OR epidemiologic risk (outbreak, travel)

Influenza Testing

When to test for influenza in CAP
→ When influenza is circulating in the community

Preferred influenza test
→ Rapid molecular (NAAT) rather than antigen test

Procalcitonin

Role of procalcitonin in deciding whether to start antibiotics
→ Should NOT be used to withhold antibiotics

Reason procalcitonin is unreliable in CAP
→ Low sensitivity and overlap between viral and bacterial CAP

Site of Care Decisions

Preferred severity score for deciding admission
→ Pneumonia Severity Index (PSI)

CURB-65 recommendation strength
→ Conditional (less preferred than PSI)

Major ICU admission criteria for CAP
→ Vasopressor-dependent shock OR mechanical ventilation

Severe CAP definition
→ 1 major criterion OR ≥3 minor IDSA/ATS criteria

Major criterion #1
→ Septic shock requiring vasopressors

Major criterion #2
→ Respiratory failure requiring mechanical ventilation

Minor Criteria (NEED ≥3)

Respiratory rate threshold
→ ≥30 breaths/min

Oxygenation criterion
→ PaO₂/FiO₂ ≤250

Radiographic criterion
→ Multilobar infiltrates

Mental status criterion
→ Confusion or disorientation

Renal criterion
→ Uremia (BUN ≥20 mg/dL)

White blood cell criterion
→ Leukopenia (WBC <4,000/µL)

Platelet criterion
→ Thrombocytopenia (platelets <100,000/µL)

Temperature criterion
→ Hypothermia (core temp <36°C)

Hemodynamic criterion
→ Hypotension requiring aggressive fluid resuscitation

RR OPENS COLD BP

RR ≥30, O₂ (PaO₂/FiO₂ ≤250), Pressure low (needs fluids), Extra lobes (multilobar), Neuro confused, Creatinine surrogate (BUN ≥20), Low WBC, Low platelets, Cold (<36°C)

R → Respiratory rate ≥30, R → Reduced oxygenation (PaO₂/FiO₂ ≤250), O → Opacities (multilobar infiltrates), P → Platelets <100,000, E → Encephalopathy (confusion/disorientation), N → Nitrogen (BUN ≥20 mg/dL), S → Shock physiology (hypotension needing fluids), C → Cold (temperature <36°C), L → Leukopenia , D → (memory filler — disease severity)(WBC <4,000), B → Blood pressure low (aggressive fluids), P → (reinforces hypotension)

Outpatient Antibiotics

First-line outpatient CAP treatment without comorbidities
→ Amoxicillin OR doxycycline

When macrolide monotherapy is acceptable
→ Only if local pneumococcal resistance <25%

Outpatient CAP with comorbidities: preferred strategies
→ β-lactam + macrolide/doxycycline OR respiratory fluoroquinolone

Inpatient Antibiotics (No MRSA/Pseudomonas Risk)

Nonsevere inpatient CAP empiric therapy
→ β-lactam + macrolide OR respiratory fluoroquinolone

Severe inpatient CAP empiric therapy
→ β-lactam + macrolide OR β-lactam + fluoroquinolone

β-lactam monotherapy for inpatient CAP
→ Not recommended

MRSA / Pseudomonas Coverage

HCAP category status in 2019 guideline
→ Abandoned

Empiric MRSA/Pseudomonas coverage recommendation
→ Only if locally validated risk factors present

MRSA empiric options
→ Vancomycin OR linezolid

Pseudomonas empiric options include
→ Piperacillin-tazobactam, cefepime, meropenem, etc.

Role of MRSA nasal PCR
→ Negative test supports de-escalation

Aspiration Pneumonia

Routine anaerobic coverage for suspected aspiration
→ Not recommended

When to add anaerobic coverage
→ Lung abscess or empyema

Corticosteroids

Steroids in nonsevere CAP
→ Not recommended

Steroids in severe CAP
→ Generally not recommended

Steroids in influenza pneumonia
→ Not recommended

Steroids acceptable in CAP
→ Refractory septic shock per Surviving Sepsis Campaign

Influenza-Associated CAP

Influenza-positive CAP: antiviral therapy
→ Oseltamivir recommended (inpatient strong, outpatient conditional)

Influenza-positive CAP: antibacterial therapy
→ Should still be started initially

Duration of Therapy

Minimum antibiotic duration for CAP
→ At least 5 days

Criteria to stop antibiotics
→ Clinical stability (vitals, mentation, PO intake)

MRSA or Pseudomonas CAP duration
→ 7 days

Follow-up Imaging

Routine follow-up chest X-ray after CAP resolution
→ Not recommended

When follow-up imaging may be appropriate
→ Persistent symptoms or lung cancer screening candidates