Sputum smear is diagnostic if?

Ans. (c) > 25 neutrophils and <10 squamous epithelial cells* Expectorated sputum is necessarily contaminated by upper respiratory secretions as it passes through the oropharynx and mouth.* When examining the Gram stain of such a specimen, the examiner should determine whether it is mostly purulent material from the lung or mainly saliva.* Since squamous epithelial cells line the upper airway but not the tracheo-bronchial tree, their presence indicates that upper airway secretions have contaminated the specimen to some degree.* Several criteria have been proposed for determining that a sputum specimen is not excessively contaminated with oropharyngeal flora and is therefore acceptable for culture.* For example:# Fewer than 10 squamous epithelial cells per field when viewed through a low-power (10x) lens (total magni- fication 100x) and more than 25 neutrophils per low-power field, or- a ratio of neutrophils to epithelial cells greater than 5:1* Even if the specimen conforms to those standards, the patient doesn't necessarily have pneumonia.* That diagnosis depends upon clinical and radiographic information. Patients with viral bronchitis, chronic obstructive lung disease, or tracheal intubation, for example, can have purulent sputum with a predominant organism in the absence of infection of the lung parenchyma.* In some clearly satisfactory sputum specimens collected from patients with pneumonia due to a single organism (e.g., Streptococcus pneumoniae), not only is the infecting organism visible with Gram stain, but often small numbers of other types of bacteria are also present.* A common mistake is to conclude that the Gram stain shows "mixed flora" and therefore does not help establish a diagnosis.