How Reliable is Laboratory Testing?

Laboratory testing is subject to many influences that could adversely affect the integrity of the result 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-Analytical is the term used to describe things that happen from the time the test is ordered to the time the sample arrives in the lab.
• Analytical is the term used to describe the things that happen during the handling and analysis of the sample in the laboratory.
• Post-Analytical is the term used to describe what happens after a result is obtained and includes how and when it is reported to your provider.

Pre-Analytic Activities
From the instant a test is ordered, a chain of events is set into motion. All these steps must be done the right way to assure that an acceptable sample arrives at the lab. The following are some of the areas where errors can occur, and standard procedures are in place to prevent such errors.

• Test ordering process – the provider or a staff member must order the correct test using the correct name or code.
• Patient preparation for the test – the patient should have received appropriate instructions about diet, fasting, medications, etc. to assure that the sample will not contain substances that interfere with the test.
• Patient identification – the person collecting the sample needs to confirm that the person is indeed the patient on whom the test was ordered. In hospitals, this means checking for a wrist band and confirming proper identification of the patient.
• Completeness of patient information - the sample must be carefully labeled with two identifiers (usually patient name and date of birth or medical record number) to assure that the sample is associated with the patient and not another person with the same name.
• Specimen collection procedures - the sample must be collected in the correct type of container and mixed with the right preservative. The lab staff who collect samples receive special training on how to collect samples for each kind of test.
• Transport to the lab - some samples need to be kept cold, some need to arrive within a limited time, so careful handling and prompt transportation are important components to sample integrity.

Automated ordering systems are increasingly used to minimize errors in sample collection and test requests. Use of computer technology (Laboratory Information System or LIS) allows health care providers to quickly input the test orders themselves, minimizing the chance for misunderstanding and error. These systems can generate labels that include a bar code for tracking and identification and can provide supplemental information on the size sample needed, types of containers or blood tubes to be used to collect the sample, and information about handling and transport.

One of the key steps in getting correct results is identifying the person from whom the sample is collected and the sample itself correctly. Safety guidelines call for using at least two different identifying methods (such as name and patient ID number) for both identifying the person and their sample. When you are asked to give your name and some other identifying information, it is to assure that you and your sample are correctly matched. If this isn’t done when a sample is taken, make sure you check to see that your sample is identified correctly.

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 and lipids are checked). A patient who does not follow preparation instructions or provides insufficient information to the health care 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, including the following:

• Instrument operations – all instruments are calibrated and tested regularly according to a standard protocol that addresses quality control, maintenance, and operation.
• Valid test reagents – all test materials have an expiration date. The lab has routine procedures to make sure that test materials are good and have not gone past their expiration date.

Many test methods use automated analyzers, thus minimizing opportunities for human error. Bar code readers read the sample tube label and associate the result with the correct patient. A robotic system carefully removes the exact amount of blood or urine needed for the test. The onboard computer monitors the test as it is in progress to assure that there are no unexpected occurrences during the analysis. Most instruments have internal computer surveillance systems to detect malfunctions or other discrepancies and bring them to the attention of the laboratory staff.

Post-Analytic Activities
After the test is completed and the result generated in the lab, there are systems to deliver it in a timely fashion to the health care provider.

• Report sent to appropriate party – the report needs to be sent to the provider who ordered the test and any other health care professional identified to receive the report.
• Timely reporting of data – there is an expected turn around time (TAT) for test results, with more critical results and results for monitoring of acute events needed more promptly than routine tests. Labs have a hierarchy of tests that are critical and special codes that can be used to assist in meeting medically necessary TAT.
• Reference intervals included - lab reports do not simply report a test result without providing a framework for interpreting the result – the “reference range.” Some lab computer systems can also suggest diagnoses, follow-up testing, and other insights that may help the provider interpret the result.
• Immediate notification of results exceeding “critical limits” - each laboratory has in place a system for immediate reporting to the ordering physician any finding that reflects a critical or life-threatening condition.

Most laboratory results are collated and managed by a sophisticated computer system capable of sending electronic reports to the health care provider by directly printing the report in a physician’s office, by email, or by automated faxing. These computers can alert laboratory staff of an unusual finding, such as a critical value, and can alert the staff to call the physician. Laboratory reports generated by the system can also highlight values outside the expected or reference range to help the physician focus on the tests that are of most concern.