From the Guidelines
Sputum culture is indicated in patients with suspected bacterial pneumonia, bronchiectasis, or chronic obstructive pulmonary disease (COPD) exacerbation, particularly when empiric antibiotic treatment fails or when a specific pathogen is suspected 1. It is also recommended for patients with cystic fibrosis, immunocompromised individuals, or those with a history of recurrent respiratory infections 1.
Key Indications for Sputum Culture
- Suspected bacterial pneumonia
- Bronchiectasis
- COPD exacerbation
- Cystic fibrosis
- Immunocompromised individuals
- History of recurrent respiratory infections
Additional Considerations
- Patients with symptoms such as persistent cough, fever, or hemoptysis 1
- Patients who require hospitalization for respiratory illness 1 The culture should be performed before initiating antibiotic therapy, if possible, to ensure accurate results 1. In patients with suspected nontuberculous mycobacterial (NTM) pulmonary disease, sputum culture is essential for diagnosis, and multiple positive cultures may be required to confirm the diagnosis 1.
From the Research
Indications for Sputum Culture
The following are indications for a sputum culture:
- Patients with an acute exacerbation of chronic obstructive pulmonary disease (COPD) and purulent sputum 2, 3, 4
- Patients with COPD exacerbations and certain clinical characteristics, such as:
- Low FEV1 (< 35% predicted or < 50% predicted) 2, 3, 4
- Bronchiectasis 3
- Long-term oxygen therapy 3
- Low body mass index (BMI) (< 22 kg/m2) 2
- Severe exacerbations in the preceding year requiring hospitalization 2
- High Acute Physiology and Chronic Health Evaluation (APACHE) II score 2
- Use of inhaled steroids 2
- Patients with Gram-negative bacteria on sputum smear, sputum purulence, high body temperature, low albumin level, and high dyspnea grade 4
- Patients with early treatment failure or repeated exacerbation when antibiotic treatment is started 5
Sputum Culture Results
Sputum culture results can be used to:
- Identify the presence of bacterial pathogens, such as Haemophilus influenzae and Streptococcus pneumoniae 2, 3, 4
- Guide antibiotic therapy, with a change in antibiotic therapy induced by microbiological results in a significant proportion of cases 3, 5
- Predict clinical response to antibiotics, although the relationship between sputum culture results and clinical response is not always clear 4
Limitations of Sputum Culture
The following are limitations of sputum culture:
- Sputum colour reported by patients is not a reliable marker of the presence of bacteria in acute exacerbations of COPD 6
- Sputum culture is not always necessary for outpatients with AECOPD, and examining Gram-staining and purulence on sputum smear may be sufficient to predict the presence of bacterial pathogens 4