Microscopic Examination of Gram-Stained Sputum: A Neglected Laboratory Modality

To the Editor—Published nearly simultaneously, an article from my laboratory [1] and the excellent systematic review of sputum Gram stain (GS) results in diagnosing community-acquired pneumonia (CAP) by Ogawa et al [2] reached important and similar conclusions, namely that microscopic examination of Gram-stained sputum can reliably identify causative bacteria. Both studies dealt only with high-quality sputum, which, admittedly, can be obtained from only a minority of patients. Our study required samples with >20 white blood cells (WBCs) per epithelial cell and excluded patients who had received antibiotics for >16 hours; two-thirds had received ≤2 hours of treatment. Reasons for mistrusting results of GS include (1) reliance on poor-quality samples; (2) analyzing specimens after prolonged antibiotic administration [3]; and (3) the assumption that a culture result of so-called normal respiratory flora (NRF) should be ignored. Ogawa et al reported only on the utility of...