Medical Assistant Exam: Clinical Procedures - Laboratory Testing and Collecting and Processing Specimens

Collecting and processing specimens for testing is an important duty of the medical assistant. The timing of the collection, the processing, and the method used are all geared toward giving the physician accurate results.

Blood Samples
Venipuncture, also known as phlebotomy, is the removal of a sample of blood, usually from a superficial vein. The procedure is performed to obtain a blood sample for analysis, or as a source for blood donation. A dermal puncture is a removal of blood from the capillaries. This collection procedure is used when a small quantity of blood is needed or when the patient’s vein is too small or fragile for a venipuncture.
A venipuncture is most frequently performed using the veins in the antecubital space of the forearms and the inside of the elbow. Another site that can be used is the back of the hand.
Blood may be drawn from a vein using one of two methods. Blood may be drawn directly into an evacuated tube, a glass or plastic tube sealed with a rubber stopper, using a multi-sample needle. Alternately, blood may be drawn using a needle and syringe, which is a tube attached to the needle. In the evacuated-tube method, the vacuum inside the tube provides the pressure to pull blood out of the vein. In the syringe method, manual pressure on the plunger pulls blood from the vein.

Venipuncture Equipment
Having the proper equipment and supplies at hand is one of the keys to being able to perform a fast and easy blood draw. The most common method of drawing blood is using evacuated tubes. The following equipment is necessary for an evacuated tube blood draw:
- Needles: A needle for drawing blood must have a large enough opening to prevent damage to the red blood cells, or hemolysis. Different needles are used for a single sample or for multiple samples; a multiple-sample needle has a rubber sheath that fits over the end of the needle and penetrates the rubber stopper of the evacuated tube so that blood does not leak out while the tubes are being changed. The medical assistant should choose the needle length that is easiest to control, using a combination of personal preference and an evaluation of the stability of the vein.
- Winged infusion set: A winged infusion set, or butterfly needle, can be used on pediatric patients, the elderly, and patients with small or difficult veins. It can be attached either directly to a syringe or to an adapter that screws into a plastic holder for use with evacuated tubes. This allows more tubes to be drawn.
- Needle holder: A needle holder is a cylinder that the needle is screwed into. Needle holders come in different sizes to accommodate the size of the collection tube.
- Tourniquet: A tourniquet is a thin strip of nonlatex rubber used to tie around the arm to help locate a vein. The tourniquet is tied three to four inches above the elbow and should not be left on for more than one minute because of the risk of hemoconcentration, or a decrease in the fluid components of the blood.
- Alcohol: An alcohol swab is used to clean the site before the venipuncture to prevent infection.
- Gauze and tape: Gauze is used to absorb blood after the venipuncture and to aid in applying pressure to the site. Adhesive tape is used to secure coverage to the venipuncture site.
- Evacuated tube: A tube with air evacuated from it to create a vacuum. When using the evacuated-tube method, a plastic holder holds the needle in place and supports the evacuated tube(s). The vacuum in the tube draws the blood into the tube. Each tube fills with blood until the vacuum is exhausted.

Some tubes contain one or more additives, depending on the test that will be done on that sample. The stopper color identifies the additive in the tube. Different brands of evacuated tubes (called systems) have a different color coding. The medical assistant must learn and remember the color-coding for the particular system used in any office in which he or she works. Blood drawn by the syringe method is usually put into an evacuated tube for transport to the lab.
Tubes with no additives are used to allow a clot to form. These are used to perform tests on chemicals in the serum (the liquid portion of the blood after all of the cells and clotting elements have settled and formed a clot). These include blood chemistry analyses such as tests for the presence of glucose, cholesterol, electrolytes, therapeutic drugs, alcohol and street drugs, hormone measures, and serology.

BLOOD COLLECTION TUBES
Color - Additive - Tests

yellow - sodium polyanethol sulfonate - blood or body fluid cultures
light blue - sodium citrate - coagulation
red - none - chemistry, serologic, toxicology
gold or tiger - silica particles to enhance clot formation - chemistry, serologic
green - heparin - chemistry
lavender - ethylenediaminetetraacetic acid (EDTA) - hematology
gray - potassium oxalate or sodium fluoride - chemistry

This chart is an example of a system of color coding for evacuated tubes.
If blood analysis cannot be done immediately, a tube with a silica gel (called a serum separator tube, or SST) is used. This tube must be centrifuged as soon as possible after clot formation. After centrifuging, the gel separates the serum from the cells. Separating the serum from the blood cells prevents the cells from altering the chemistry of the serum.

Order of Draw
The order of draw refers to the order in which tubes are filled when multiple tubes are collected for multiple blood studies. The following order is recommended to minimize problems if small amounts of additives from a previous tube get into tubes drawn later.

1. Sterile tubes for blood culture

2. Tubes without additives

3. SSTs—tubes that contain silica gel

4. Tubes for coagulation studies. If only coagulation studies are ordered, a tube without additives should be drawn first (and discarded) to prevent tissue thromboplastin from entering the tube for coagulation studies.

5. Other tubes containing anticoagulants

6. Other tubes with additives

Sites to Avoid
Evacuated tube method: The evacuated tube method is appropriate for medium and large veins. The best veins are the median cephalic or lateral basilic veins the antecubital area. Do not use scarred, sclerosed, or injured veins, or veins in areas with a rash, bruise, tattoo, or other skin lesion, or an arteriovenous fistula for renal dialysis.
If a patient has had a mastectomy (removal of the breast), do not draw from the arm on the side of the removed breast. Do not draw from an edematous area (an area of swelling due to fluid collection). Do not draw from the arm in which an intravenous drip (IV) is in place.
To avoid needle-stick injuries, the medical assistant should never recap a needle. An available sharps container or one of the safety devices designed for blood drawing should always be used. These include holders that slides down to enclose the needle after use or needles that blunt while still in the vein. A hemolyzed blood specimen or one taken from an atypical area, such as a hematoma or the area above or below an intravenous drip, shows marked differences in many tests.

Syringe method: The syringe method is appropriate for small and delicate veins. The syringe method should be used on the veins of the antecubital area. A 22G or 23G, 1' to 11/2' needle should be used. Only about 10 mL of blood can be obtained using this method.
The blood must be transferred from the syringe to evacuated tubes before it clots. For safety, use a blood transfer device. Attach the transfer device to the syringe. Insert an evacuated blood collection tube into the transfer device/syringe assembly. Next, allow the blood to transfer from the syringe to the tube using the tube’s vacuum. Do not depress the plunger of the syringe. When the appropriate number of tubes is filled, dispose of the syringe and transfer device as one unit according to your institution’s policies.

Dermal Puncture
A dermal, or skin puncture, is performed to obtain capillary blood. Capillaries are the small blood vessels that carry blood to and from the small arterioles to the tissues and return blood to the small venules. Common sites used for dermal puncture include the ring or middle finger (called a finger stick) and the plantar surface (underside) of the heel. The finger stick is most common.
Any blood test can be performed with blood from a capillary specimen, but not enough blood is obtained for multiple tests or for repeating a test to confirm results. Capillary specimens may be taken on infants and children when small amounts of blood are needed or when it is difficult to perform venipuncture because of inaccessible or collapsed veins.

Equipment and Supplies
To obtain a capillary blood specimen, the following equipment and supplies may be used:
1. Lancet, to pierce the skin. Manual lancets are single blades for making small incisions—disposable lancets are used for adults and a disposable automatic lancet is used for an infant. A disposable lancet is placed in a plastic holder and the system’s platform is placed on the patient’s finger. A plunger is depressed and the spring causes the lancet to puncture the skin. The advantage of such a system is that it standardizes the depth of puncture.
2. Blood collection device. Microhematocrit or capillary tubes are either plastic or glass-coated with a plastic sheathing to minimize the risk of shattering. Capillary tubes can be either plain or heparinized to avoid blood clotting. They are closed by pressing one end in sealing clay. Microcollection containers are small plastic tubes with removable, color-coded caps. The tip is shaped like a scoop, to direct the blood flow off the side and down the tube. The color of the cap may indicate the type of additive, if any, in the tube. For instance, a lavender-colored top indicates there is EDTA in the tube, as in evacuated tubes.

3. Alcohol pads and gauze pads

4. Sealing clay

Finger sticks are usually performed on the middle or ring finger of the nondominant hand. There is good capillary flow in this area and enough subcutaneous tissue to prevent accidental puncture of the bone (as might occur on the little finger). A finger stick should not puncture deeper than 3.1 mm on an adult or 2.4 mm on an infant or child.

Urine Specimens
Urine specimens are used for a variety of tests and collected in a variety of ways, the most common of which are discussed here.

Routine or Random Specimen
Random urine specimens can be used for a variety of tests, including urine pregnancy tests and urinalysis. Random specimens are not recommended when a UTI is suspected.
To collect a random urine sample, the patient should be instructed to void into the specimen cup, filling the cup with approximately 50 mL to 100 mL of urine. After the specimen is collected, the container must be tightly capped to avoid leaking. If the patient is unable to void, he or she should be instructed to drink water and try to eliminate later, perhaps after the physical examination.

Clean-Catch Midstream Specimen
Collection of clean-catch midstream urine is the method of choice for most healthcare providers. This type of specimen, if properly collected, provides an excellent sample for most urine tests. A clean-catch midstream specimen can be used for routine urinalysis, urine cultures, urine pregnancy testing, and microscopic examination, as well as for culture and sensitivity testing. It may be helpful to post instructions for clean-catch specimens in appropriate urine collection sites.

First Morning Specimen
When a concentrated urine specimen is needed, as in pregnancy testing, the first morning sample is the specimen of choice. Formed elements and urine chemicals such as nitrites are best studied at that time. Unless the patient is hospitalized, first morning specimens must often be collected by the patient at home. Label the specimen cup with the patient’s name and give it to the patient with explicit instructions and any necessary supplies before the patient leaves the office.
The patient should be instructed to deliver the specimen as soon as possible, no more than four hours after the urine is collected. If the specimen cannot be transported immediately to the testing facility, it should be refrigerated.

24-Hour Urine Specimen
The 24-hour urine collection can be used for a number of tests. One of the most important factors affecting the specimen collection is determining the specific container in which the specimen will be collected. A laboratory test reference guide should be consulted whenever a 24-hour urine test is ordered. Some 24-hour procedures require the addition of a preservative into the container before the specimen is collected; other tests use no preservative but require that the specimen be refrigerated between voids.
If a preservative is added to the 24-hour specimen container, the container must be labeled as to the type and amount of preservative added. Most tests require that urine specimens be protected from light. Also, the total volume or weight must be carefully measured and recorded.

Containers
Three different types of containers are used for collecting urine specimens. Urine cups for single samples can be either sterile (for culturing urine) or nonsterile (for random specimens to conduct general urinalysis). Urine containers for 24-hour collection are larger and may contain preservatives, such as boric acid or hydrochloric acid. The medical assistant should always check the procedure manual to determine which preservative to add before giving the collection bottle to the patient.

Stool Specimens
A stool, or fecal, specimen is collected to test for bacteria and/or parasites if a patient’s chief complaint is persistent diarrhea that does not respond to the usual treatment. It can also be collected for an occult blood test, to see if there is hidden blood in a patient’s stool.
Fecal collection can be accomplished either by using a rectal swab or by collecting a portion of a bowel movement. The methods for collecting a specimen from a bowel movement are discussed here.
- Adults: For adults who are capable of using a toilet, the method of collection is fairly straightforward. The toilet should be covered with a large sheet of plastic wrap. A depression in the middle of the plastic wrap should be made to allow for collection. Following the bowel movement, part of the stool should be collected using the collection spoon.
- Infants: Collecting a specimen from a diaper is also straightforward. The diaper should be lined with plastic wrap. Once the stool specimen has been provided, use the collection spoon to add sufficient stool to the collection vials.

In both cases, a specimen spoon is used to collect the specimen, and enough stool should be collected so that, when inserted into the specimen vial, it will bring the liquid level to the fill line.
If a large volume of specimen is collected, such as a 24-hour fecal fat specimen, the total volume or weight must be accurately measured and recorded.

Sputum Samples
A sputum sample may be necessary to diagnose tuberculosis, pneumonia, or other infectious disease of the lungs and lower respiratory tract.
Expectoration is the coughing up of mucus from the lungs and throat. This is the least uncomfortable method of sputum collection for the patient and is used when the patient is able to produce sputum by coughing. If the expectoration method is to be used, the patient should be instructed to drink plenty of liquid the night before, not to brush his or her teeth or use mouthwash in the morning, and to give the specimen before eating. The patient should be instructed to take a deep breath and cough vigorously to obtain the lower respiratory secretions. The patient should never simply spit into the specimen cup, as saliva is not composed of lower respiratory secretions and is not appropriate for a sputum specimen.
Suctioning equipment can also be used to collect a sputum sample. The medical assistant will require special training for the use of this equipment.

Throat Culture Specimens
To obtain a throat culture, a tongue depressor is used to hold the tongue down and a sterile swab. The specimen is obtained with a sterile swab from the back of the throat; care must be taken not to touch the tongue or teeth after the specimen is obtained.
The test is performed either by growing a culture in an incubator or by using a rapid strep test kit, which will be discussed in detail further in the chapter. If the rapid strep test is negative, a culture is recommended. To cause the least discomfort to the patient, a medical assistant should take specimens on two swabs simultaneously, rather than having to swab the throat twice.

Vaginal Specimens
A vaginal culture is collected using a swab. The sterile polyester tipped swab contains a preservative (buffer) to maintain the integrity of the specimen. The laboratory will test the specimen for bacteria, viruses, or fungal infections.
During a speculum examination by the physician, and prior to any examination or manipulation of the cervix or vaginal tract, the swab is lightly rotated across the posterior fornix of the vagina for approximately ten seconds to absorb cervicovaginal secretions. The swab is then removed and placed into the plastic sleeve.

Wound Specimens
A wound specimen is a specimen from a cut or surgical incision that has become infected. A wound may contain aerobic or anaerobic bacteria. Aerobic bacteria require oxygen to survive, whereas anaerobic bacteria thrive under conditions without oxygen. Deep wounds are especially likely to contain anaerobic bacteria. It is important that specimens be collected to perform aerobic and anaerobic cultures. Gram stains should also be performed on all wound specimens.
Use a sterile swab to collect a specimen from a wound that appears to be infected when directed to do so by the doctor. The specimen collected must be a true representative sample. A swab for a wound culture collected from the surface of the wound generally does not yield the same results as one taken from the depths of the wound.

Processing Specimens
Processing the specimen is as important as the collection. If the specimen is not processed properly it could lead to inaccurate results and unnecessary risk to the patient.

CDC Guidelines
Infection with biohazardous material can occur during specimen collection, handling, transporting, or testing. Potentially infective specimens include blood, body tissue biopsy specimens, urine, exudates, and bacterial cultures and smears. Infection can occur through aspiration of a pathogen, accidental inoculation by a needle stick, aerosols created by uncapping specimen tubes, centrifuge accidents, and entry of pathogens through cuts and scratches.
The CDC recommends safety precautions regarding handling of all patient specimens. These precautions include an infection control plan, engineering and work practice controls, personal protective clothing and equipment, sufficient training and education, provision of hepatitis B vaccination, and medical intervention after exposure incidents.
The Clinical and Laboratory Standards Institute (CLSI) also has guidelines for the laboratory worker with regard to protection from blood-borne illness caused by contact with patient specimens. The CAP offers a voluntary accreditation program for clinical laboratories that includes biosafety measures. One important precaution that can be taken is labeling of potentially biohazardous material.
Washing the hands is undoubtedly the most effective means of preventing infection. Information on proper hand washing technique can be found at the beginning of this chapter under 'Medical Asepsis.'

Specimen Handling and Preservation
It has been said that the results of laboratory testing are only as good as the specimen sent for testing. Specimens that are handled improperly after collection may provide erroneous results, causing unnecessary compromise to the patient’s health.
The following are reasons why a specimen might be rejected by a lab:
- quantity not sufficient (QNS)
- hemolyzed specimen
- specimen collected in the wrong container
- unlabeled specimen
- contaminated specimen
- delay in transport

All microbiology specimens should be transported as soon as possible to the laboratory. Transport media, such as CO2 ampules or capsules for anaerobic bacteria, should be activated. For instance, culture tubes are activated by squeezing the sides of the culture tube to release the holding fluid.
Urine specimens must be refrigerated if they cannot be transported immediately.

Proper Labeling
Proper labeling and transport protocols are important for accurate microbiology testing results. A label must include:
- patient’s correct name
- patient identification number, or a bar code
- site of the specimen collection
- type of culture ordered (e.g., throat culture for beta strep, vaginal culture for gonorrhea)
- date and time of the specimen
- doctor’s name
- initials of the person performing the specimen collection

Quality Control
Quality assurance (QA) is a comprehensive set of policies and procedures utilized to assess the reproducibility of a test result. Quality control (QC) is a process to ensure the validity or accuracy of test results.
Every POL, or physician office laboratory, needs to establish a quality assurance, quality control, and clinical standards program to monitor its performance and improve in areas in which it determines it is deficient.

QC Testing
Quality control is a method of ensuring that all factors involved in the testing procedure at a POL are performing as expected. The factors assessed include:
- personnel
- manufactured test kits or reagents
- instruments
- supplies

Manufacturers prepare a sample of a tested substance that has a known value, or a positive or negative outcome; this is known as a control reagent. If the medical assistant is responsible for performing QC procedures in the POL, he or she will run the control sample as if it were a patient’s specimen and compare the results with the expected values provided by the manufacturer of the control reagents. A positive control should yield a positive result and a negative control should produce a negative result. Some controls such as glucose controls have numerical values. The expected value is provided as a range. As long as the control falls within the range, the testing procedure can be used for patients.

Possible reasons for faulty test results include:
- Human error. If the test is run manually, human error can cause incorrect results.
- A problem with the chemicals or reagents being used. Chemicals and reagents should always be checked to see if they have expired or are otherwise bad. Reagents may get contaminated with bacterial growth from improper use.
- A problem with the laboratory equipment. In situations where automated testing equipment is used, control samples are sometimes run along with the patient samples; other times, the samples are run first and results checked to see if they are within the acceptable range.
For many pieces of automated testing equipment, QC tests are performed first thing in the morning, before running patient specimens, and at regular intervals throughout the day or after a certain number of tests have been run. Results of QC tests are recorded in the QC log. Instruments should be cleaned daily and preventive maintenance should be performed according to the manufacturer’s recommendation.