Effect of sputum induction by hypertonic saline on specimen quality

Area of Science:

• Pulmonary Medicine
• Microbiology
• Diagnostic Testing

Background:

• Microbiologic work-up of sputum is crucial for diagnosing pulmonary infections.
• Sputum specimens can be contaminated by saliva, affecting diagnostic accuracy.
• Hypertonic saline inhalation is a theoretical method to enhance bronchial secretions and improve sputum quality.

Purpose of the Study:

• To compare the quality of sputum obtained via hypertonic saline induction versus spontaneous expectoration in patients with respiratory tract infections.
• To evaluate the impact of sputum induction on specimen quality, using established laboratory criteria.

Main Methods:

• A laboratory-blinded, randomized study design was employed.
• Patients with respiratory tract infections and productive cough were enrolled.
• Sputum quality was assessed by the ratio of polymorphonuclear neutrophils (PMNs) to squamous epithelial cells (SECs) and a Gram stain quality (Q) score.

Main Results:

• No significant difference was observed in the PMNs/SECs ratio between induced (65%) and spontaneous (74%) sputum groups (p = 0.47).
• Similarly, the Q score criterion (>= +1) showed no significant difference, with 55% in the induced group and 66% in the spontaneous group meeting the threshold (p = 0.37).
• These findings indicate that sputum induction by hypertonic saline did not enhance specimen quality.

Conclusions:

• Sputum induction with hypertonic saline inhalation does not improve the quality of expectorated sputum specimens for microbiologic analysis.
• Current methods of sputum collection for diagnosing pulmonary infections may require further optimization beyond simple saline induction.