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May 04, 2024

Specimen collection 4: procedure for obtaining a sputum specimen

This article, the final part in a four-part series, describes the rationale and procedure for collecting a sputum specimen Citation: Shepherd E (2017) Specimen collection 4: procedure for obtaining a

This article, the final part in a four-part series, describes the rationale and procedure for collecting a sputum specimen

Citation: Shepherd E (2017) Specimen collection 4: procedure for obtaining a sputum specimen. Nursing Times [online]; 113: 10, 49-51.

Author: Eileen Shepherd is clinical editor at Nursing Times.

Obtaining a specimen involves collecting tissue or fluids for laboratory analysis or near-patient testing, and may be a first step in determining a diagnosis and treatment (Dougherty and Lister, 2015). Specimens must be collected at the right time, using the correct technique and equipment, and be delivered to the laboratory in a timely manner (Dougherty and Lister, 2015). Box 1 provides a reminder of the general principle of specimen collection. These are discussed in more detail in part one of this series (Shepherd, 2017).

Box 1. Professional issues and good practice principles

Nurses must:

The specimen must be:

The collection of any tissue/fluid carries a risk to staff from splash or inoculation injury, so standard precautions should be followed (Loveday, 2015).

Mucus production in the respiratory tract is a normal process. It is secreted from goblet cells found in the surface epithelium lining the airways of the respiratory tract and from seromucous glands in the connective tissue layer beneath the mucosal epithelium.

The primary functions of mucus are to:

Sputum expectoration is abnormal and there is always an underlying pathological cause. Such causes include:

Secretions in the lower airways create an ideal environment for the growth of bacteria (Dougherty and Lister, 2015) and the presence of infection can increase and change the nature of mucus leading to the need to expectorate and cough.

The aim of sputum collection is to identify the bacterial, viral or fungal cause of a suspected infection and its sensitivities to antibiotics. A specimen is indicated if patient has:

It is difficult to accurately assess the amount of sputum produced but it may be described by its colour and consistency. It is important to consider the characteristics of sputum as part of an overall patient assessment. Sputum may be described using the following terms (Richardson, 2003), which can aid diagnosis of the cause:

Yellow, orange or green sputum is commonly associated with bacterial or viral infection (Dougherty and Lister, 2015). Red sputum indicates the presence of blood and may suggest tuberculosis or cancer (Richardson, 2003), or infection, particularly in bronchiectasis and fungal growths such as aspergilloma in immunocompromised patients. Expectorating large amounts of white frothy sputum may be a sign of pulmonary oedema.

Sputum samples can be obtained using a non-invasive or invasive method and ideally should be collected before antibiotics are started. Invasive methods include oropharyngeal or endotracheal suctioning; these are used with patients who are intubated. A sputum trap is connected to the suction catheter to collect the sputum (Fig 1) (Brekle, 2017).

Obtaining sputum using suctioning requires specific skills and nurses need to be aware of potential side-effects, including hypoxia, cardiac instability and mucosal trauma (Dougherty and Lister, 2015). This article describes non-invasive methods.

It is important to note that droplets and aerosols may be generated when collecting sputum specimens, so health professionals should use personal protective equipment as stipulated in local policies (includinggloves, apron and face masks) (Brekle, 2017).

Patients should be provided with an explanation of the specimen required, pointing out the difference between oral secretions and sputum. They should be instructed to sit up and take several deep breaths to loosen secretions before giving a deep cough to release the sputum. Ideally, the specimen should be no less than the size of a small fingernail.

It is important to assess whether patients experience pain related to respiration – particularly when coughing, for example following chest or abdominal surgery, as this can prevent them taking deep breaths and expectorating. Analgesia should be given and their pain reassessed before attempting to collect a specimen. Patients should also be encouraged to support any wounds using their hands or a pillow (Dougherty and Lister, 2015).

Prescribed nebulised sodium chloride 0.9% can help to loosen secretions before specimen collection (Dougherty and Lister, 2015). Physiotherapists can also assist patients with coughing techniques and can teach other clinical staff the active cycle of breathing techniques to help with chest clearance.

Ensuring the patient is well-hydrated can help increase sputum production and the likelihood of obtaining a useful sample.

Ideally specimens should be obtained in the morning as secretions pool in the lung overnight, providing an environment in which bacteria can replicate (Dougherty and Lister, 2015); this is particularly important when testing for tuberculosis. Collecting the sample before breakfast also reduces the risk of contaminating the sample with food. Patients should be advised to not clean their teeth or use a mouthwash before specimen collection as this may kill the bacteria.

It is important to check that the sample contains sputum, as samples contaminated with oropharyngeal secretions and saliva are difficult to interpret and can be misleading (Brekle, 2017). Contamination of the sample can result in inappropriate or delayed treatment.

Assemble equipment including:

Professional responsibilitiesThis procedure should be undertaken only after approved training, supervised practice and competency assessment, and carried out in accordance with local policies and protocols.