Assessing the Quality of Sputum Samples

Direct gram stain is one of the commonest stains used to ascertain whether a specimen accurately represents the infection location. Sputum sample examination has been carried out using gram stain for suspected pulmonary infections. The quantity and proportion of segmented neutrophils present reflect the degree and nature of the inflammatory response.
Bartlett has devised a grading system for evaluating sputum samples. In accordance with this system, a smear is given a negative value when squamous epithelial cells are seen, signifying contamination with oropharyngeal secretions. Segmented neutrophils are given positive values, indicating that inflammation is currently active. A final score of 0 or below means that the specimen is invalid since there was either no inflammatory response or there was considerable salivary contamination.
Murray and Washington have proposed a similar grading scheme. The samples are invalidated by the abundance of epithelial cells in groups 1 to 4 of this system, which suggests contamination with oropharyngeal secretions. Only specimens from group 5 are regarded as having clinical relevance.
With a few exceptions like pulmonary infections brought on by mycobacteria, the majority of fungi, Legionella spp., and viruses cannot be diagnosed using the sputum grading system. The importance of polymorphonuclear neutrophils is also modified in a few circumstances, such as: When the patient is neutropenic from disease/ongoing therapy or patient does not mount an effective inflammatory response or foreign body causes irritation to a mucosal surface like endotracheal catheter.
If the specimen is found to be less than ideal, the doctor should be called and a replacement specimen should be requested.It is crucial to convey that the presented specimen will not provide useful information regarding potential pathogens from the lower respiratory tract. Continue culturing the specimen only if it is found to be a good quality lower respiratory tract specimen.
In summary, a Gram stain should be carried out to assess the specimen's quality prior to culture. One of the two criteria should be utilized to identify the contamination.Use the grading system and review in accordance with the laboratory specifications.