Collecting Samples for Laboratory Testing
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Today’s technologies allow testing on an impressively wide variety of samples collected from the human body. Most often, all that is required is a blood sample. However, samples of urine, saliva, sputum, feces, semen, and other bodily fluids and tissues also can be tested.
For some samples, they can be obtained as the body naturally eliminates them. Others are quick and easy to acquire because they reside in the body’s orifices. For some, minor surgery and anesthesia give the health practitioner access to the required sample.
You may notice on this web site that some tests can be performed on more than one type of sample. For example, glucose testing can be performed on both blood and urine samples. However, the sample used for testing is often determined by the purpose of the particular test: a blood glucose test is used to help diagnose diabetes and monitor blood glucose levels in diabetics while urine glucose is one of the substances tested when a urinalysis is performed, such as when a urinary tract infection or kidney disorder is suspected. Sometimes there are options for the type of sample, such as with HIV antibody testing (blood, urine, and oral fluid screening tests are available), and in other situations, one particular type of sample is required.
Samples naturally eliminated from the body
Some samples such as urine, feces, and sputum can be collected as the body naturally eliminates them, while semen can be collected by the patient. Collection of some samples from young children or patients with physical limitations may require assistance. Usually, collecting these samples is painless, but obtaining them can occasionally be awkward and unpleasant because they involve elimination of bodily wastes and involve body parts and functions people prefer to keep private.
Sometimes these types of samples can be collected at home and brought to a medical office or facility, but they also may be collected at a medical facility such as a doctor’s office, clinic, laboratory patient service center, or hospital. These facilities are usually designed to minimize sample handling by the patient and embarrassment. You may, for example, find a “pass-through” window in the bathroom so you don’t have to walk the hall with a see-through container you have just filled. You may find printed instructions on how to obtain urine or stool samples posted in the bathroom so you don’t have to listen to a nurse tell you explicitly how to obtain a “clean catch” of urine or a fecal sample. If you are sensitive to these issues and want to choose a healthcare provider or testing center that provides such options, you can ask about their procedures, their layout, and steps taken by the staff to ensure patient privacy and comfort.
Below are examples of types of samples typically collected by the patient. It is very important that all instructions for sample collection are carefully followed. Make sure you understand the instructions before collecting your specimen.
Male patients ejaculate into a specimen container, avoiding lubricants, condoms, or any other potentially contaminating materials. Usually, men need to refrain from ejaculating for at least 2 days prior but less than 7 days before collecting the specimen. The specimen must not be refrigerated but kept as close to body temperature as possible by placing the container in a pocket and delivering it to the laboratory within 60 minutes.
Patients are instructed to cough up sputum from as far down in the lungs as possible. (A health practitioner may assist the patient in some situations.) This is best accomplished first thing in the morning before eating or drinking, by taking several deep breaths before expectorating into the collection cup. Sputum should be relatively thick and not as watery as seen when producing saliva.
Patients usually collect this sample themselves during toileting, following instructions to prevent the sample from becoming contaminated from other material in the toilet bowl. Patients may also be told to avoid certain foods during the test period. Depending on the test, patients may be instructed to collect the sample in a container, scoop a small portion into a vial, or smear a small amount on special test paper. Wash your hands well after handling the sample.
Most urine specimens are collected by having the patient urinate into a container or receptacle. To keep the sample from becoming contaminated by materials outside the urinary tract, patients are given instructions on how to clean the genital area and void a bit of urine before collecting the specimen into the container. (If a urinary catheter is required, a health practitioner is usually responsible for insertion.) Collecting the urine specimen is awkward but not in itself uncomfortable (An infection, however, can create a burning sensation during urination.). For certain tests, 24-hour urine samples are collected at home and must be refrigerated during the collection process. Remember to wash hands well after collecting the specimen.
This type of sample may be collected using a swab or, if a larger volume is needed for testing, patients may be instructed to expectorate into a container without generating sputum.
This is a combination of saliva and oral mucosal transudate (material crossing the buccal mucosa from the capillaries) that is also collected from the mouth. For example, a rapid HIV test uses oral fluid. The patient collects the sample by using a special device to swab around their outer gums.
This type of sample may be collected using a special sweat stimulation procedure that is painless and allows sweat to be collected into a plastic coil of tubing or onto a piece of gauze or filter paper. It is then analyzed for the amount of chloride in the sweat. Elevated levels of chloride suggest a diagnosis of cystic fibrosis.
Samples that are easy to obtain
Some samples are collected by simply running a swab over the affected area. Procedures of this type can be performed in a clinic, in your doctor’s office, or at the hospital bedside. The sample may be sent to a laboratory for analysis (although a few tests can provide in-office results in just a few minutes). Throat, nasal, vaginal, and superficial wound cultures, for example, are obtained in this way. The procedures, while they may sometimes be uncomfortable, are generally quick, relatively painless, and have no after-effects.
Secretions and tissues from the female reproductive system
Samples of vaginal secretions are obtained by running a cotton swab over the walls of the vagina; cervical cells for a Pap test are obtained using a cotton swab and spatula or a tiny brush. Endometrial tissue samples are obtained by inserting a thin, flexible, hollow tube into the uterus, during which you may feel a slight pinch or brief cramping. Patients may feel some emotional and physical discomfort during this procedure. A sensitive approach by the healthcare provider contributes greatly to the patient’s emotional comfort. If you are physically uncomfortable, discuss this with your healthcare provider.
Secretions and fluids from the nose or throat
The specimen is collected by running a swab over the area of interest and processed for testing, such as cultures. People typically respond to swabbing of their throat with a momentary “gag” reflex. If the throat is sore, the sample collection, brief as it is, can be uncomfortable. Similarly, a nasal swab may be a bit uncomfortable as the swab is inserted and reaches areas inside the nose that are typically never touched. Try to remember that the discomfort is temporary and ask your practitioner if there are ways to minimize any soreness that may result.
Samples from open wounds and sores
If a wound or sore is located in the outer layer of skin, the specimen is typically collected on a swab by brushing the swab over the area and gathering a sample of fluid or pus. Touching the open wound area may be temporarily painful since the wound is likely to be tender and sore. If a wound or infection is deep, however, a needle and syringe may be used to aspirate a sample of fluid or pus from the site.
Samples from within
Some samples can only be obtained by breaking through the body’s protective coverings (e.g., skin). Blood specimens are obtained in minimally invasive procedures conducted by specially trained physicians, nurses, or medical personnel. Collection of tissue specimens is a more complex process and may require a local anesthetic in order to obtain a specimen.
Because of the nature of these collections techniques, some pain or discomfort may be involved. Knowing what the procedure involves may help alleviate some anxiety when having to undergo these types of sample collections. For more on this, see the article Coping with Test Pain, Discomfort, and Anxiety.
Blood samples can be collected from blood vessels (capillaries, veins, and sometimes arteries) by trained phlebotomists or medical personnel. The sample is obtained by needle puncture and withdrawn by suction through the needle into a special collection tube. Some specimens may be obtained by a finger puncture that produces a drop of blood, such as that used for glucose testing. The procedure usually takes just a few minutes and hurts just a bit, typically when the needle is inserted or from the puncture of a lancet. See Tips on Blood Testing for more information.
Samples of tissue may be obtained from a number of different body sites, such as breast, lung, lymph node, or skin. Depending on the site and the degree of invasiveness, some pain or discomfort may occur. The time required to perform the procedure and for recovery can also vary greatly. These procedures are conducted by healthcare providers who have had specialized training. Tissue biopsies can be collected using procedures, such as:
- Needle biopsy — A needle is inserted into the site and cells and/or fluid are withdrawn using a syringe. A slight pinch may be felt at the site of needle insertion. Usually no recovery time is required and slight discomfort may be experienced afterwards.
- An excisional biopsy is a minor surgical procedure in which an incision is made and a portion or all of the tissue is cut from the site. A closed biopsy is a procedure in which a small incision is made and an instrument is inserted to help guide the surgeon to the appropriate site to obtain the sample. These biopsies are usually performed in a hospital operating room. A local or general anesthetic is used, depending on the procedure, so the patient remains comfortable. If a general anesthetic is used, recovery may take one to several hours.
Cerebrospinal fluid (CSF)
A sample of cerebrospinal fluid is obtained by lumbar puncture, often called a spinal tap. It is a special but relatively routine procedure. It is performed while the person is lying on their side in a curled up, fetal position or sometimes in a sitting position. The back is cleaned with an antiseptic and a local anesthetic is injected under the skin. A special needle is inserted through the skin, between two vertebrae, and into the spinal canal. The health practitioner collects a small amount of CSF in multiple sterile vials; the needle is withdrawn and a sterile dressing and pressure are applied to the puncture site. The patient will then be asked to lie quietly in a flat position, without lifting their head, for one or more hours to avoid a potential post-test spinal headache. The lumbar puncture procedure usually takes less than half an hour. Discomfort levels can vary greatly. The most common sensation is a feeling of pressure when the needle is introduced. Let your healthcare provider know if you experience a headache or any abnormal sensations, such as pain, numbness, or tingling in your legs, or pain at the puncture site.
Other body fluids
Other body fluids such as synovial fluid, peritoneal fluid, pleural fluid, and pericardial fluid are collected using procedures similar to that used for CSF in that they require aspiration of a sample of the fluid through a needle into a collection vessel. These are generally more complex type of collections and often require some patient preparation, use of a local anesthetic, and a resting period following sample collection. For details, see the descriptions for arthrocentesis, paracentesis, thoracentesis, and pericardiocentesis.
The bone marrow aspiration and/or biopsy procedure is performed by a trained healthcare specialist. Both types of samples are most often collected from the hip bone (iliac crest). In some instances, marrow collection may be collected from the breastbone (sternum). Almost all patients are given a mild sedative before the procedure, then asked to lie down on their stomach or side for the collection. The site is cleaned with an antiseptic and injected with a local anesthetic, treating it as a typical surgical field. When the site has numbed, the health practitioner inserts a needle through the skin and into the bone. For an aspiration, a syringe is attached to the needle and bone marrow fluid is aspirated. For a bone marrow biopsy, a special needle is used to collect a core (a cylindrical sample) of bone and marrow. Even though the patient’s skin has been numbed, the patient may feel brief but uncomfortable pressure (pulling and/or pushing) sensations during these procedures. After the needle has been withdrawn, a sterile bandage is placed over the site and pressure is applied. In some instances, the procedure may be repeated on the opposite hip (bilateral bone marrow), most often done as part of the initial diagnostic workup. The patient is then instructed to lie quietly until their blood pressure, heart rate, and temperature are normal, and then to keep the collection site dry and covered for about 48 hours.
A sample of amniotic fluid is obtained using a procedure called amniocentesis to detect and diagnose certain birth defects, genetic diseases, and chromosomal abnormalities in a fetus. Amniotic fluid surrounds, protects, and nourishes a growing fetus during pregnancy. A sample (about 1 ounce) of amniotic fluid is aspirated by inserting a thin needle through the belly and uterus into the amniotic sac, collecting both cellular and chemical constituents that are analyzed to detect certain genetic abnormalities that may be present.
NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used. To access online sources, copy and paste the URL into your browser.
Sources Used in Current Review
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Interviews (professional titles and positions are listed as they were at the time of the interviews)
Rebecca Elon, MD, MPH. Medical Director of North Arundel Senior Care, Severna Park, Maryland.
Joy Goldberger, MS, CCLS. Education Coordinator, Child Life Department, Johns Hopkins Children’s Center, Baltimore, Maryland.
Saralynn Pruett, MT (ASCP). Phlebotomy Supervisor, Department of Laboratory Medicine and Pathology, Mayo Foundation, Rochester, Minnesota.
Karen Szafran, CPNP. Nurse practitioner, pediatric practice, Alexandria, Virginia.
Myra Daly, PT (ASCP). Phlebotomy Supervisor, Northwest Community Healthcare, Arlington Heights, Illinois.
Joan Kosiek, MT(ASCP)SH. Point-of-care consultant, Northwest Community Healthcare, Arlington Heights, Illinois.
Richard Flaherty. Executive Vice-President, American Association for Clinical Chemistry, Washington, District of Columbia.