Diagnostic Tests Study Guide for the Medical Assistant test

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Laboratory Procedures

Laboratory procedures are put into place to ensure the best quality care for patients and to protect laboratory staff. Be familiar with policies and procedures pertaining to handling of equipment and specimens.

Training Requirements

Each laboratory has training requirements to be completed before use of the lab is permitted. Knowledge of policies, procedures, and use of equipment is needed.

Normal and Abnormal Results

All results of testing must be reported. Results are often reported electronically in most facilities. Each facility has a protocol for reporting critical values. If your facility deems a specific result critical, it must be immediately reported to the physician or nurse.

Patient Preparation

For each lab specimen to be collected, there is a process for obtaining the specimen correctly. Sometimes, patient preparation is required. For example, when obtaining blood intravenously, the site of needle insertion must be properly cleaned using an appropriate antiseptic. Know patient preparation for different specimen collection processes.


Be familiar with the terminology associated not only with lab tests but with equipment as well. Understand the meanings of common abbreviations, and be familiar with patient diagnoses.

CLIA-Waived Point of Care Testing

Point of care testing is testing that has been approved to be performed at the patient’s bedside. Know the procedure for collecting different specimens, such as urine, stools, or blood.

Microhematocrit and hemoglobin: Put simply, hematocrit and hemoglobin are results obtained through blood testing that determine how much blood is in the body. Hemoglobin is a protein on RBCs that aids in the transport of oxygen. Depending on these results, a patient may require a blood transfusion.

Blood glucose: Obtaining a blood glucose level can be done in a couple of different ways. Patients may use their own personal monitors at home to get results. Results can also be obtained through a blood test, or use of a facility’s glucometer. If using a glucometer, be sure to follow the control procedure listed for the equipment before obtaining a patient specimen.

Sedimentation rate: Sedimentation rate is a blood test that detects inflammation in the body. If drawn regularly, this blood test can help physicians monitor inflammation and track patient decline or improvement.

Urine: There are several different ways to collect a urine specimen. Be familiar with sterile, clean-catch, and catheter collection procedures. Also, know the procedure for using a pediatric urine collector and how these terms relate to urine collection and testing: physical, chemical, microscopic, and culture.

Other Tests

There are other tests that are not as commonplace as the ones listed above. Even so, be familiar with the reason for testing and protocols for collecting specimens.

Mononucleosis: This is usually caused by the Epstein-Barr virus. Blood tests can be used to look for antibodies to this virus.

Rapid group A Strep, Throat: A swab of the throat is obtained to diagnose this bacterial infection.

C-reactive protein (CRP): CRP is a blood test used to determine inflammation in the body.

HCG pregnancy: HCG is a hormone made during pregnancy. It can be detected in the urine or blood. HCG is the hormone that is detected by at-home pregnancy tests.

H. pylori: A bacteria usually found in the stomach, it often requires an esophagogastroduodenoscopy (EGD) to get samples from the lining of the stomach.

Chain of custody collections: Chain of custody collections require a paper trail showing evidence of specimen collection, analysis, and disposal. For example, some employers perform random urine drug screenings. Other uses for this type of test are paternity testing, blood alcohol level, and tests done in conjunction with forensic studies.

Wound: Wounds with or without drainage are swabbed with a designated swab and sent to the lab to be cultured.

Sputum: Sputum collections involve the patient coughing up phlegm into a designated sterile container.

Viral, Influenza: A nasal swab is done to diagnose a flu virus.

Stool: The patient should be instructed to defecate in a clean collection container. Afterward, the nurse or nursing assistant will collect a stool specimen in the appropriate container for lab analysis.

Nasal; nasopharyngeal: Nasal swabs are similar to swabbing for the flu, except it is not required that the patient be swabbed as far into the nasal passage.

Semen: The patient should be instructed to ejaculate into a provided sterile container.

Specimen Processing

Specimens must be processed according to proper procedure to ensure testing accuracy. The process begins with collecting specimens according to protocol.

Preparing Specimens

After specimens are collected according to protocol, the processing and analysis continues.

Slide preparation

Know the process for preparing slides for viewing under a microscope. There are some solutions that may be applied to fast moving specimens to slow them for viewing.

Culture plate preparation

After cultures are collected and prepared, the environment for bacteria or yeast growth must be maintained. This includes the use of equipment such as incubators.


Labeling specimens is as important as collecting them. Without appropriate labeling, specimens are typically thrown out and recollection is necessary. Review what information is required on a specimen label.

Sources of Contamination

Contamination of specimens can happen at any point during the specimen collection and analysis process. The best way to prevent contamination of specimens is to practice good hand hygiene.


Formaldehyde is the most common fixative for preserving specimens. The commonly used fluid preservative is alcohol. Specimens such as urine are preserved by way of refrigeration. Review other methods for preserving specimens.


Recordkeeping is a major part of tracking lab specimens and lab results. Keeping a written record of research and development of specimens is useful. Records should be kept of processes and results.

Other Procedures

Be familiar with laboratory equipment such as incubators, centrifuges, and microscopes and know what they are used for. For example, a centrifuge is a machine used on laboratory blood tubes to separate the components of the sample.

Handling and Transportation

Some medications or specimens must be transported within a specific time frame. Some are light-sensitive and require transport in colored containers. For example, blood has a certain amount of time in which it must travel from the blood bank and into the patient. Be aware of specific instructions for different products or specimens.


Communication is very important and can impact a patient’s care, even if indirectly. When giving instructions to non-lab personnel or transporter, be very clear in your instruction for the product or specimen. Clear communication is also necessary for lab results. Results must be reported to a nurse or the physician promptly to ensure quality patient care.

EKG/ECG Testing

EKG, sometimes called an ECG, stands for electrocardiogram. This test is usually used to diagnose a heart rhythm in a patient who is experiencing chest pain or discomfort. Know the proper procedure for lead placement and be familiar with basic heart rhythms.

Various Tests

EKGs and cardiac stress tests are commonly used to help diagnose a heart condition. EKGs are performed to show a heart rhythm that a patient is having, and allows healthcare personnel know if there is an abnormality with the heart. Stress tests are done to measure the heart’s response to external stimuli. Review the processes of each test.

Patient Preparation

Before testing can be done, the patient must be prepared for the upcoming tests to ensure accuracy. For example, an updated list of patient medications would be helpful before performing a stress test. Certain medications can alter the results of the test. While performing an EKG test, the patient must be lying still, in supine position, for accurate results.

Lead Placement

On many EKG machines, a diagram of the lead placement is illustrated. However, be sure to know where to place each lead, as poor or improper placement can alter the results of the test.

Additional Equipment

There is other equipment used in cardiac testing that is frequently overlooked. Review steps of use for other testing equipment such as treadmills and blood pressure cuffs.

Holter Monitor

A Holter monitor is used if a patient requires long-term cardiac monitoring. Sometimes, the monitor is used for 24 hours and, in some cases, it can be used for several weeks. The patient will receive instructions on how to use and care for the monitor before leaving the hospital or office.

Patient Directions

It is very important to provide thorough and easy-to-understand directions to patients. It is helpful to have them repeat the instruction back to you to ensure understanding. Answer any and all questions the patient may have.

Special Patient Considerations

Every patient is different and special cases must be considered. For example, a patient with special needs may have to be given clearer, step-by-step directions to perform testing, or an amputee may not be able to undergo the treadmill portion of a stress test. Be mindful of the patient’s state of health and try to anticipate special needs for patients, including those in isolation and patients with pacemakers.

Monitoring Patient During Test

During testing, a patient may begin to experience chest pain, shortness of breath, or other complications. Review EKG rhythms and know how to monitor heart rate and blood pressure. Be familiar with the cardiac cycle, examine the waveform, and know how to respond to complications and life-threatening arrhythmias.

Capture Results

Before capturing results, be sure all leads are in the appropriate place and there is no artifact. If there is interference in the reading, check lead placement and patient position until an accurate reading is recorded.

Other Terms and Concepts

Become familiar with the definition and role of these terms in EKG testing and tracing evaluation:

  • Mounting techniques
  • Mounting to patient’s chart; transmitting to physician
  • Calculate heart rate and cardiac cycle from tracings
  • Rhythms and arrhythmias: sinus, atrial, ventricular, junctional
  • Inspect waveforms for symmetry, direction, and amplitude (P waves, QRS complexes, ST segments, T waves)
  • Heart conduction from the EKG tracing [e.g., PR-interval (PRI), QRS duration, QT-interval]
  • Waveform variance and cause: ischemia, injury, or infarction


EKG recordings can be affected by a number of situational occurrences. It is important to know what causes an incorrect recording and how to arrange for accurate results. Several common reasons for inaccurate EKG readings include improper patient positioning, improper lead placement, or poor lead contact. Sometimes, the adhesive on the electrodes becomes dry and brittle, which may result in a poor reading. In patients with hairy chest and back areas, it is sometimes necessary to shave the patient in order to obtain good lead contact.

Know the function of these in problematic EKG tracings:

  • Standardization mark range
  • Wandering baseline
  • Somatic issue
  • Electrical issue
  • Special considerations: shunts, piercings, scars, pacemaker/AICD-failure to pace
  • Paper speed (25mm, 50mm)
  • Machine sensitivity ( h, 1, 2)
  • Proper grounding
  • Proper cleaning and storage
  • Paper supply and placement
  • Lead reversal
  • Patient movement or seizures
  • Battery charge

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