For many people, clinical laboratory testing is an unfamiliar side of medical care. Yet many of the decisions you and your healthcare provider make about your health status – obtaining a diagnosis, developing a course of action for treatment, or monitoring your body’s response to therapy – are based on laboratory data. Your
provider trusts the results coming from the laboratory and that trust is well-placed. Clinical laboratory testing is held to very high state and federal regulatory standards. All laboratory test methods must meet scientifically rigorous criteria before they can be used in clinical practice. For commercial tests in the U.S., the Food and Drug Administration (FDA) reviews the scientific evidence to ensure that: For more on the regulation and evaluation of test development, see the article Putting New Laboratory Tests into Practice. A laboratory must demonstrate that it is able to perform that test in a clinically acceptable way. State and federal regulatory agencies monitor the laboratory and set standards that a laboratory must meet in order to be allowed to perform the test.
Some of these standards are: These requirements ensure that the tests
performed by clinical laboratories for patient care will generate results that are reproducible and can be trusted. For additional details on standards set for laboratories, see the article Lab Oversight: A Building Block of
Trust. Some of the statistical indicators that are used to assure that both the test method and the laboratory performing the test are meeting acceptable standards are described in the next few pages, along with descriptions of other ways in which laboratories assure reliability. In addition, read the article on
Reference Ranges and What They Mean, which provides additional details on specific concepts and practices that contribute to the trust placed in laboratory tests. Four indicators are most commonly used to determine the reliability of a clinical laboratory test. Two of these, accuracy and precision, reflect how well the test method performs day to day in a laboratory. The other two, sensitivity and specificity, deal with how well the test is able to distinguish disease from absence of disease. The accuracy and precision of each test method are established and are
frequently monitored by the professional laboratory personnel. Sensitivity and specificity data are determined by research studies and are generally found in medical literature. Although each test has its own performance measures and appropriate uses, laboratory tests are designed to be as precise, accurate, specific, and sensitive as possible. These basic concepts are the cornerstones of reliability of your test results and provide the confidence your healthcare provider has in using the
clinical laboratory. Accuracy and Precision Statistical measurements of accuracy and precision reveal a lab test’s basic reliability. These terms, which describe sources of variability, are not interchangeable. A test method can be precise (reliable reproducibility) without being accurate (measuring what it is supposed to measure and its true value) or vice versa. Accuracy
(Trueness) Precision (Repeatability) Although a test that is 100% accurate and 100% precise is ideal, in practice, test methodology, instrumentation, and laboratory operations all contribute to small but measurable variations in results. The small amount of variability that typically occurs does not usually detract from the test’s value and statistically is insignificant. The level of precision and accuracy that can be obtained is specific to each test method but is constantly monitored for reliability through comprehensive quality control and quality assurance procedures. Therefore, when your blood is tested more than once by the same laboratory, your test results should not change much unless your condition has changed. There may be some differences between laboratories in precision and accuracy due to different analytical instrumentation or methodologies, however, the test results are reported with standardized reference intervals specific for that laboratory. This helps your healthcare provider to correctly interpret the information and its relevance to that reference interval. Sensitivity and Specificity The tests that a provider chooses in order to diagnose or monitor a medical condition are based on their inherent ability to distinguish whether you have the condition or do not have the condition. Depending on the symptoms and medical history, a provider will order tests to confirm a condition (tests with high sensitivity) or tests to rule out the condition (tests with high specificity). Sensitivity Specificity The FDA requires that developers and manufacturers of a new test provide target values for test results and provide evidence for the expected ranges as well as information on test limitations and other factors that could generate false results. Thus it is critical for the healthcare provider to correlate the laboratory results with an individual’s clinical condition to determine if repeat testing would be needed. Quality ControlLaboratory testing is subject to many factors that potentially could adversely affect the integrity of the sample and prevent the timely reporting of an accurate test result to your provider. Typically these are grouped into three areas that track the sample from beginning to end of the process.
Pre-Analytic Activities
Automated ordering systems are increasingly used to expedite orders and minimize errors in sample collection and test requests. Use of computer technology (Laboratory Information System or LIS) allows healthcare providers to quickly input the test orders themselves. Since there are thousands of laboratory tests that may be selected from a laboratory’s test menu, this process minimizes the chance for misunderstanding of what tests are desired. Many of these systems can generate labels that include a bar code for tracking and identification of a patient and the specific tests ordered. It can also provide supplemental information on the sample size needed (how much blood needs to be drawn), types of containers or blood tubes to be used to collect the sample, and information about handling, transporting, and storing samples. For some tests, your diet, medications, and exercise history are important for proper interpretation of results. In some cases, special preparation must be taken to get reliable results for a test (such as fasting overnight before blood glucose or cholesterol is checked). A patient who does not follow preparation instructions or provides insufficient information to the healthcare provider undermines the entire quality assurance effort for a specific test. Analytic Activities Once the specimen is received in the laboratory, quality assurance procedures guide and monitor all related activities and include the following:
Post-Analytic Activities
Most laboratory results are collated and managed by a sophisticated computer system (Laboratory Information System or LIS) capable of sending electronic reports to the healthcare provider by directly printing the report in a provider’s office with a dedicated printer, by email, or by automated faxing. These computers can track test orders, provide pre-analytical information, assist in quality control and quality assurance procedures, alert laboratory staff of an unusual finding such as a critical value, and report and store all laboratory results. Laboratory reports generated by the system can also highlight values that fall outside the expected or reference interval to help the provider focus on the tests that are of most concern. Here is one example of a laboratory report containing the elements described above. The Role of Testing in the Diagnostic ProcessA healthcare provider is expected to evaluate all of the relevant findings – laboratory test data plus information from other sources, such as physical exam, personal and family histories, signs and symptoms, and other diagnostic examinations, i.e., X-rays, EKG, etc. – before settling on a diagnosis and developing a treatment plan. Given the complexities in human physiology and disease response, no diagnosis should ever be made solely on the basis of a single lab test. The clinician must always ask, “Do the test data fit with the other pieces of the puzzle?” Careful evaluation and consideration of test findings increase the reliability of a diagnosis and can reduce the chance of medical errors. Data from medical tests are part of the information set that needs to be considered when a healthcare provider makes a diagnosis. When a laboratory report indicates abnormal or unexpected results, it is incumbent on your healthcare provider to further evaluate and corroborate the information at hand to ensure an accurate diagnosis. If the data do not correspond with the clinical picture, additional information may be needed and retesting may be appropriate. In some situations, the progression of the disease or condition may not be evident for the testing modality to be relevant. Is there anything I can do? Yes. Sometimes there are things you do or don’t do that can affect your tests results. Following a couple of guidelines can help to ensure that your results are interpreted correctly by your healthcare provider:
If you and your provider are surprised by a test result, here are some questions you could discuss together.
ConclusionLaboratory testing is a science professionally conducted with rigorous statistical analysis, quality controls, and extensive oversight. Medical testing is an important component in the diagnostic tool kit of a healthcare provider. However, it is most reliable when used in conjunction with other meaningful data collected in the diagnostic process, when appropriate questions are asked and answered, and when there is open communication between healthcare teams and patients. You can put great trust in the data generated by today’s exacting medical tests. A caveat to remember is that a diagnosis and treatment plan for a serious disease should never be based on a single medical test. Test findings are just one of the pieces of the diagnostic puzzle. Help your healthcare provider with the interpretation of the data by providing thorough information on your medical history and keeping track of symptoms you wish to report. To reduce the chance that you are improperly diagnosed and given potentially harmful and unnecessary medical procedures, first follow test preparation instructions carefully and tell your healthcare provider and the person collecting your sample about any exceptions you made. Accessing your lab report after you have testing done is a good way to stay informed and you can follow up with your healthcare provider if you have any questions concerning your results. Related ContentView SourcesSources Used in Current Review Sanford KW, McPherson RA. Preanalysis, in Henry’s Clinical Diagnosis and Management by Laboratory Methods, 22ed (2011).McPherson RA, Pincus MR, eds. Elsever-Sanders: Philadephia. Chapter 3, pp 24-36. Khalsa AK, Santa Cruz M, Saubolle MA. Principles of preanalytic and postanalytic test management, in Clinical Laboratory Management, 2nd ed. Garcia LS, ed. Am Society for Microbiology: Washington, DC (2014). Chap 26, Pp 488-505. Sources Used in Previous Reviews Forsman, Rodney. The Value of the Laboratory Professional in the Continuum of Care. Clinical Leadership & Management Review. November/December 2002. Pp. 370-373. Otto CN. “Identification of criteria for a report card to evaluate clinical laboratory testing services.” CLMR 16(1):7-16, 2002. Nowakowski R (1992). A Review of Theoretical and Practical Aspects of Clinical Laboratory Testing. Optometry Clinics. Vol. 2; issue 1: pp. 1-14. Oppenheim IA (1972). Textbook for Laboratory Assistants. CV Mosby Co., Saint Louis: p. 20. Barnett RN (1971). Clinical Laboratory Statistics. Little, Brown and Co., Boston: P. 9. Hood W. (1980). A-Z of Clinical Chemistry. Halsted Press, New York: pp. 2 and 291. Stiene-Martin EA, Lotspeich-Steininger CA, Koepke JA, eds. (1998). Clinical Hematology: Principles, Procedures, Correlations. Lippincott-Raven Publishers, Philadelphia: Pp. 565-576. The Johns Hopkins Consumer Guide to Medical Tests (2001). Margolis S, editor. Medletter Associates, Inc., New York: P. 36. Fernandes JJ (December 1991). Realistic Expectations of Laboratory Testing. Journal of the American Osteopathic Association. Vol. 91; issue 12: Pp. 1223 and 1228. Wurman S (2001). Diagnostic Tests for Women. TOP, Newport, RI: P. 3. Goldmann DR (1999). American College of Physicians Complete Home Medical Guide. Dorling Kindersley Ltd., New York: P. 213. Woods MA (1994). The Clinical Medical Assistant. WB Saunders Co, Philadelphia: Pp. 183-187. Abbott Laboratories, product insert, aHIVAB. Available online at http://www.abbottdiagnostics.com/getPDF.cfm?controlNumber=344038. Diagnostics Enable Medical Information Age; Improving Health Care Decisions. Presentation by AdvaMed to the House of Representatives, May 11, 2006. Available online at http://www.advamed.org/publicdocs/news_event_ald_act2006.shtml. American Society of Clinical Pathologists. Lab Facts. Available online at http://www.ascp.org/general/labweek/guidefacts.asp. Accessed 3/1/02. Mayo Foundation for Medical Education (October 25, 2000). Headline Watch: Colorectal Cancers and DNA Testing. Available online through http://www.mayoclinic.com. Accessed 3/6/02. Mayo Foundation for Medical Education (January 23, 2001). Pap Smear: Simple, Lifesaving Test. Available online through http://www.mayoclinic.com. Accessed 3/6/02. Get the latest lab testing news & updates from our bi-monthly newsletter Your privacy is important to us What is the medical assistant's role in coordinating laboratory tests and results?The medical assistant working in the physician's office laboratory collects samples, performs tests, follows strict procedures, manages quality control, maintains laboratory equipment, keeps accurate records, prepares specimens for transport to reference or off-site laboratories, and reports results to the physician.
What should a medical assistant do with a critical lab value :?A typical policy for the appropriate response to a critical value is that someone from the laboratory must notify by telephone a physician, nurse, physician assistant, or medical assistant at the ordering location.
What should the medical assistant do as follow up if a patient calls to request laboratory results?What should the medical assistant do as follow-up if a patient calls to request laboratory results? If a paper medical record system is used, find the medical record and attach the message to the record. If a patient calls to request a medication refill, which information should always be included in the message?
What are typical roles that a medical assistant may assume in a clinical laboratory?Examples of laboratory duties include: collecting and processing urine specimens, collecting and processing blood specimens, collecting and processing throat cultures, performing CLIA Waived tests, and collecting and processing Drug Screens.
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