Sputum is obtained for analysis to identify pathogenic organisms and to determine whether malignant cells are present. It also may be used to assess for hypersensitivity states (in which there is an increase in eosinophils). Periodic sputum examinations may be necessary for patients receiving antibiotics, corticosteroids, and immunosuppressive medications for prolonged periods because these agents are associated with opportunistic infections. In gen-eral, sputum cultures are used in diagnosis, for drug sensitivity testing, and to guide treatment.
Expectoration is the usual method for collecting a sputum spec-imen. The patient is instructed to clear the nose and throat and rinse the mouth to decrease contamination of the sputum. After taking a few deep breaths, the patient coughs (rather than spits), using the diaphragm, and expectorates into a sterile container.
If the sputum cannot be raised spontaneously, the patient often can be induced to cough deeply by breathing an irritating aerosol of supersaturated saline, propylene glycol, or some other agent delivered with an ultrasonic nebulizer. Other methods of collecting sputum specimens include endotracheal aspiration, bronchoscopic removal, bronchial brushing, transtracheal aspira-tion, and gastric aspiration—usually for tuberculosis organisms. Generally, the deepest specimens (those from the base of the lungs) are obtained in the early morning after they have accumulated overnight.
The specimen is delivered to the laboratory within 2 hours by the patient or nurse. Allowing the specimen to stand for several hours in a warm room results in the overgrowth of contaminant organisms and may make it difficult to identify the organisms (es-pecially Mycobacterium tuberculosis). The home care nurse may assist patients who need help obtaining the sample or who can-not deliver the specimen to the laboratory in a timely fashion.