Sputum is a thick mucus produced in the lungs and lower airways, distinguishing it from saliva. This substance is a mixture of mucus, immune cells, and debris coughed up from the respiratory tract. Collecting a sputum sample is a common diagnostic tool used to identify the cause of respiratory infections or diseases, such as pneumonia, tuberculosis, or chronic lung conditions. Analyzing the sample helps medical professionals identify specific pathogens like bacteria or fungi, guiding the selection of effective treatment.
Standard Collection Through Natural Expectoration
The most common method for obtaining a sputum sample is natural expectoration, where the patient coughs up the material on their own. For the best results, collection is typically performed first thing in the morning immediately after waking up, before the patient has eaten or brushed their teeth. This timing is preferred because secretions accumulate in the lungs overnight, yielding a more concentrated sample.
Before attempting to cough, the patient must thoroughly rinse their mouth with plain water to remove food particles and reduce normal bacteria. It is important to avoid using toothpaste or mouthwash, as these can interfere with laboratory test results. The goal is to obtain material originating from the lungs, not saliva or upper throat secretions, which would contaminate the specimen.
To produce a deep lung sample, the patient should first take several slow, deep breaths, holding each breath for a few seconds before exhaling fully. This technique helps loosen secretions within the bronchial tubes. Following these breaths, the patient must take one final, very deep inhalation and then perform a forceful, explosive cough that originates from the chest and abdomen. A successful cough will bring up a thick, sticky specimen, ideally about one teaspoon (5 to 10 milliliters) in volume, which should be directly expectorated into the sterile collection container. The container must be held close to the mouth to avoid contaminating the outside surface, and the patient must not touch the inside of the lid or the container itself.
Medically Induced Collection Methods
If a patient cannot produce a spontaneous, high-quality sputum sample through natural coughing, induced sputum collection may be necessary. This procedure is generally performed in a clinical setting to ensure safety and proper technique. It involves having the patient inhale a sterile, hypertonic saline solution—a salt solution with a higher concentration than the body’s normal fluids—delivered via a nebulizer.
The hypertonic saline, often 3% or higher, irritates the airways and encourages secretion production from the lower respiratory tract. This irritation helps thin the mucus, stimulating a cough deep enough to bring up a diagnostic specimen. Patients with reactive airway diseases, such as asthma or COPD, may first be given an inhaled bronchodilator medication to stabilize their airways before the saline inhalation begins.
The nebulization process can take between 5 and 20 minutes, during which the healthcare provider coaches the patient to perform deep breathing and vigorous coughing. The resulting sample, which may appear thinner than naturally expectorated sputum, is collected into a sterile cup. For patients unable to cooperate with induction, more invasive procedures like bronchoscopy or tracheal aspiration may be used in a hospital environment to directly collect secretions.
Post-Collection Handling and Submission
Following a successful collection, the container must be immediately and securely capped to prevent leakage or contamination. The integrity of the cap is paramount for both safety and sample quality. The sterile container must then be clearly labeled with the patient’s full name, date of birth, and the exact date and time the specimen was collected. Accurate labeling is necessary for the laboratory to process the sample correctly and link the result to the right patient.
The sample should be transported to the laboratory as quickly as possible to ensure the viability of microorganisms, which is crucial for accurate culture results. If immediate submission is not possible, the specimen should be stored in a refrigerator (not frozen) to slow the growth of normal flora and maintain pathogen integrity. Most laboratories require the specimen to be received within 24 hours of collection, but ideally, it should arrive within a few hours for optimal analysis.