Effect of sputum induction by hypertonic saline on specimen quality

Microbiologic work-up of expectorated material is routinely used to search for the etiology of pulmonary infections, but sputum is often contaminated by saliva. Inhalation of hypertonic saline induces bronchial secretions and theoretically may improve specimen quality. We compared in a laboratory-blinded, randomized study the quality of sputum obtained either with induction by saline or without induction in patients with respiratory tract infection and a history of productive cough. The quality of sputum was considered good if the polymorphonuclear neutrophils (PMNs)/squamous epithelial cells (SECs) ratio was > or = 2 or the Q (quality) score was > or = +1 on Gram stain. Forty-nine and 50 patients were able to expectorate in the induced and spontaneous sputum groups, respectively. PMNs/SECs ratio was > or = 2 in 65% and 74% of the patients in the induced and spontaneous sputum groups (p = 0.47); for the Q score, a value > or = +1 was found in 55% and 66% of the patients of each group (p = 0.37). In conclusion, sputum induction by hypertonic saline inhalation does not improve specimen quality as judged by the PMNs/SECs ratio on Gram stain.