College of American Pathologists
 Point of Care Testing Toolkit


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Point of Care Testing Toolkit
  • Introduction & Definitions
  • Advantages & Disadvantages
  • History
  • Current & Projected Technology
  • References
  • Tools
  • Toolkit Authors
  • Pathologist Roles
  • Pathologist as Laboratory Director
  • Pathologist as Clinical Consultant
  • Pathologist’s Regulatory Role
  • Pathologist as Technical Consultant
  • Give us your feedback on this sectionPathologist as Technical Consultant:
    The Challenges of Quality Control For POCT

    1. Quality control (QC) is the periodic analysis of stabilized specimens of known concentration to assess the test system operation and accuracy. It is an essential and integral component of a Quality Management system
    2. Classical QC is usually associated with an automated analyzer where the QC checks a “run” of patient samples analyzed in a batch or over a set time period, e.g. QC run every 8 hours. Such a run typically uses a homogeneous bottle of liquid reagent to test a group of calibrators, patient specimens, and control specimens. The performance of the control results should reflect the quality of the patient results in this setting, because the test is performed from the same bottle of reagent, on the same analyzer, by the same operator, and under the same environmental conditions.
      1. If the control specimens do not recover the expected concentration within specified performance limits, the run is rejected and corrective action is undertaken before patient results are released. Control limits are adjusted to achieve a desired balance of “false positives” (rejection of a run when there has been no actual change with assay performance) and “false negatives” (failure to reject a run when either bias or random error has exceeded a certain threshold).
      2. Instrument performance can be followed by plotting of control results over time and comparing trends between multiple controls to allow detection and correction of potential performance issues before they affect the quality of patient results. QC does a good job at detecting systematic errors that persist in this setting, because the control results are affected in the same manner as patient results.
    3. Challenges of QC in the POC environment:
      1. Unit nature of POCT:
        1. While some POCT is performed with traditional automated analyzers that can test QC material in a run along with patient samples, typical POC tests are single unit ones, performed using a different strip or cartridge that may be read by any of several devices operated by multiple users.
        2. QC analyzed on one test strip/cartridge consumes the test in the process of analysis. The very next test, which may be a patient test, is analyzed by a different test strip/cartridge, and may be read by a different device and operator. So, QC results are subjected to different conditions than patient results.
        3. Performance of QC on one test cartridge doesn’t necessarily ensure similar performance on the next test.
        4. Users may need to rely on built-in control processes in conjunction with traditional QC to ensure the quality of POCT results.
    4. While QC does a great job at detecting systematic errors that affect the test system in the same way as patient samples, QC does a poor job at detecting random errors that may affect single tests, patients or samples.
    5. Fortunately, POCT devices have a variety of control processes engineered into the device to detect and prevent errors. Some of these control processes are conducted with each test while others survey the device, environmental conditions, and operator errors. For POCT, laboratories need to rely on both traditional QC and alternative control processes to ensure quality.
    6. With POCT, QC may be run at different frequencies than required in the central laboratory.
      1. For some tests, QC may be run less frequently than in a central laboratory, because other built in control processes are assessing the quality of the test, sometimes with every test performed.
      2. Other kits, or devices may require a QC sample with each sample or small group of samples tested.
      3. Some tests will require QC only once on any day when testing is being performed.
      4. For waived testing, laboratories must at least follow the minimum manufacturer requirements in the package insert for QC frequency and for performance of other control processes.
      5. The POCT Laboratory Director may want to set a more frequent schedule for QC, or implement additional control processes, especially in situations where there are many testing variables, such as high staff turnover.
        1. QC has cost and resource implications as additional reagents and staff time will be consumed that cannot be billed as patient results.
        2. Some testing sites with tight budgets and staffing may resist having to use the extra resources to perform QC, so it is important that they appreciate the costs, value, and requirements for QC before a test is implemented.
        3. Before implementing a POC test, the Laboratory Director may require that QC processes and frequencies be evaluated so that the best practices are established.
      6. The choice of control process must fit the risk of error in using any specific POCT device.
        1. Each type of device will have different risks, and necessarily require a different control strategy.
        2. Some devices may have many control processes built into the device while others may have few.
        3. Not every control process will necessarily control the entire analytical processes.
          1. Electronic controls, for instance, only assess device software, circuitry and battery functions, but do not evaluate the chemical performance of the reagents in the test strip/cartridge or the operator steps in running the test. Only “external” QC materials will do that.
      7. The laboratory must be aware of the potential sources of error from device, reagent/control and storage, patient and patient interferences, environment, and operator factors.
        1. The Laboratory Director, POCT Coordinator, and site leadership must then implement additional controls when traditional QC may not be sufficient to ensure a test meets clinical expectations.
        2. The POCT leadership team must be willing to explain and defend those decisions.
        3. An example of this situation may be in a setting where a test is infrequently run and there are many operators. POCT leadership may want operators to run a liquid QC sample with each test to ensure proper technique.
    7. Examples of POCT QC processes:
      1. Traditional QC:
        1. Glucose meters: Separate bottles of high, low (and normal) level controls are stable to an assigned expiration date if properly stored and unopened. Once opened, their expiration date changes to a new date as determined by the manufacturer, (e.g., 6 months unopened and 30 days after opening. QC must be analyzed at a frequency recommended by the manufacturer,) or whenever the meter performance is questioned or the meter is calibrated or serviced.
        2. Urine dipstick: Control materials may be liquid or dry reagents, (such as swabs that are used to create controls when placed in distilled water). Control solutions mimic both positive and negative samples for the specific component tests of the dipstick. Typically the controls are used to test each new container of dipsticks when opened, if storage conditions may have been compromised, or results are questioned.
      2. Control process is integral to test:
        1. Urine pregnancy tests contain a built in procedural control to ensure proper sample application and verify test performance. In addition, positive and negative external control solutions are typically used to test each lot/shipment of the test kit and periodically to verify performance during storage.
        2. Occult blood tests: Guaiac based card tests for fecal or gastric occult blood testing contain both positive and negative control windows that confirm if the developer is functioning as expected, identify potential false positives/negatives due to improper storage (discoloration or failure to react), and provide a visual check on the color change of a positive test to assist the user when interpreting results.
      3. Instrument control processes:
        1. Electronic: Such controls evaluate the internal electronic functions of a POC device. They may be integral to the device and are performed automatically by the instrument at set intervals or may require the use of a separate simulator that mimics the function of a test cartridge to see if the electronic sensor is reacting properly.
        2. Photometric: In instruments that perform spectrophotometric measurements of colored controls (cuvette, test strip, etc.) that are used to test light path and proper absorbance or transmittance measurement.
        3. Sample integrity: Function checks on blood gas analyzers that detect the presence of clots or bubbles in samples that would impair sensor function.
        4. Typically, POC instruments with internal control processes also require positive and negative external QC to be analyzed periodically. This should ensure the reactivity of test strips/cartridges, with each new lot or shipment and when performance of the test is questioned.
    8. Operator considerations
      1. External QC checks the test system including the operator as well as the equipment and reagents.
      2. This is especially important in the POC setting, where there may be a very large number of operators and laboratory testing represents only a small part of their duties and responsibilities.
      3. The concept of QC may be unfamiliar to POCT operators and their understanding of variables affecting test results may be limited.
      4. Administrative support for performing QC may be a challenge, especially due to the additional cost and resource burden as noted above.
      5. The POCT program must assure, to the extent possible, satisfactory results with all operators and ongoing maintenance of operator skills competency.
      6. QC may only be required once on a day of device operation and only one person may run it each day, but there may be hundreds or thousands of operators in an institution.
      7. The POCT program should ensure that all operators have the opportunity to perform QC in order to verify skills on a periodic basis (at least annually).
      8. Control processes that are built into each test, so that each test has a positive and negative control indicator, automatically provide a check of operator skills with each test.
      9. For those devices with data management, the frequency of device error codes for each operator can provide support of operator skills and verify competency or need for operator retraining.
      10. In the central lab, not only are trained technologists performing the QC, but trained supervisors are also present to oversee their performance.
        1. In the POC environment, there is less direct supervision, and indeed it may be difficult to enforce the performance of QC.
        2. Again, built-in control processes, and/or software lockout and other features that force QC performance can assist compliance with manufacturer requirements and improve test result quality better than manual tasks that the operator must remember to perform and document.
        3. Having a POCT Coordinator to educate users about QC, building processes that fit into clinical workflow and are convenient for operators, and exploiting clinical leadership partners to emphasize QC and documentation are essential.
      11. Waived testing is much more prevalent in the POC setting. Non-laboratory personnel involved in POCT have a misconception that “waived” means that QC is unnecessary and that results are always accurate.
        1. The original CLIA88 definition of waived testing may promote this misconception.
        2. Accrediting agencies have wrestled with this issue and addressed it in different ways.
      12. As a quality principle, no system is so foolproof, nor is any lab result of such trivial importance, that patient harm from an error is impossible.
        1. All devices can and will fail if subjected to the right conditions.
        2. Care is required with all laboratory tests, waived or non-waived, performed at the POC or in the central laboratory.
        3. Relatively simple and straightforward analytical systems, though, can justify less frequent liquid QC because of the variety of alternative control processes that ensure the quality of results with those systems.
        4. Manufacturers have made testing systems more robust with built-in control processes and software lock outs that ensure QC is analyzed at the frequency required before patient testing can be conducted.
        5. Connectivity solutions, such as device data management and POCT middleware systems, can also facilitate QC performance and documentation.
    9. Specimen considerations:
      1. Materials used for calibration, QC, and PT should mimic patient samples.
      2. This can be challenging in the POC setting, where the specimen might be fresh blood from a finger stick.
      3. There can be the potential for pre-analytical or analytical errors with such a complex specimen that are not reflected in testing QC materials.
        1. Sometimes QC material may have stabilizers or other materials that do not react in a similar manner to a fresh human specimen.
        2. This matrix effect can be addressed to some extent by requiring that some POC patient results be verified by simultaneous samples sent to the central lab.
          1. Checking a finger stick result against the central laboratory requires a significant volume of sample or a separate venous specimen.
          2. Comparison of different specimen types and delays in transportation of specimens to a central laboratory can affect result agreement.
      4. Alternate control processes like sample volume, clot, and bubble detection can provide some assurance that the individual specimens were not adversely impacted by gross errors in sample collection or application.
        1. Newer glucose meters have a control process that simultaneously analyzes hematocrit on each glucose test.
        2. These meters reduce the probability of a result error due to testing on a sample with too high or low a hematocrit.
        3. Unfortunately, no POCT device, developed so far, can check for hemolysis in a whole blood specimen. Thus, clinicians always need to be aware of the possibility that an abnormally elevated potassium POCT result (or worse, a seemingly normal result in a patient with true hypokalemia) is due to unrecognized sample hemolysis.
    10. Environment considerations
      1. While central laboratory analyzers operate within well-defined conditions of the hospital, POCT devices are portable and may be subjected to extremes in temperature, light, humidity, and altitude.
      2. Visiting nurses and staff that transport POCT devices or kits between locations may keep the devices and strips/cartridges in their cars or transport vehicles, resulting in exposure to freezing conditions during the winter and baking temperatures in summer.
      3. Analysis of QC after each transfer can verify test and reagent performance, but may not be practical for staff conducting frequent house calls.
      4. Manufacturers have environmental checks built into some devices that can warn operators of operation outside recommended conditions (such as ambulance drivers conducting POCT in the snow or in unheated houses).
        1. These temperature or humidity error codes prevent operation of the device and patient testing until environmental conditions have returned to normal.
        2. Unfortunately, most of these environmental checks only signal during actual operation, when conditions may have returned to acceptable levels, and do not indicate that the device and/or reagents may have been intermittently exposed to unacceptable conditions, (e.g., in the car overnight during an ice storm.)
        3. Thus, periodic analysis of QC should be relied on for verifying performance when devices or reagents may be subjected to extreme conditions or whenever results are questioned.
    11. Documentation requirements
      1. Within the central laboratory testing, the analysis of QC and documentation of control results is integral to a quality management system.
      2. Most central laboratory analyzers store control results and/or transmit the results via an interface to the laboratory information system (LIS). This allows monitoring of instrument performance through QC trends over time.
      3. In the POC environment, with the exception for some glucose meters, blood gas analyzers and coagulation devices with data management capabilities, documentation of QC results is a manual process.
      4. One of the challenges of the POC environment is assuring that users perform and record QC results as required.
        1. The creation of control logs for each POC test, clearly written QC procedures, proper training of users and periodic review of QC compliance are integral to the overall quality of a POCT program.
        2. Working with operators at clinical sites to set up documentation systems that are useful, meaningful for them and work within the clinical flow of patient care responsibilities can be helpful and build compliance.
      5. Tests with internal procedural controls may also require documentation.
        1. Each test constitutes a ‘control run’ for the test.
        2. The results of the positive and negative internal procedural control should be documented along with the test result unless, as in some POC devices, failure of the control invalidates the test, generates and error code, or blocks the device from use.
        3. Both CAP and the Joint Commission require that the results of internal procedural controls for visual end-point tests be documented in the patient record along with the test result.
      6. In the central laboratory, a QC violation will typically involve corrective actions such as recalibration, instrument maintenance, and changing the onboard reagent.
        1. No POC test should be reported when QC indicates a problem, but comprehensive troubleshooting by operators at the POC may not be practical nor appropriate under regulations for waived testing.
        2. For much of POCT, however, the central laboratory may serve as a backup, and the corrective action may simply be to cease POCT and send specimens to the central laboratory until the problem is resolved.
        3. This is another indispensible role for a POCT Coordinator.
          1. That person is the liaison and support person with POCT sites and can help troubleshoot QC problems and monitor performance trends or device problems that control processes may reveal.
          2. In some settings, the POCT Coordinator may be able to provide that support in a real time fashion or provide back-up devices or kits so that testing can continue.
        4. As with the central lab, it is crucial that clear instructions be set for failure of QC or other control process.
        5. An unacceptable practice that must be avoided is the ad hoc repetition of QC until a satisfactory result is obtained. Repeating QC once to re-test the process or reagents is appropriate, but multiple repetitions until a “correct” result is obtained will mask real underlying testing problems.
        6. Users need to learn that QC reflects test system and operator performance, and that any QC or control process error may affect the quality of patient test results.
    12. In summary, POCT devices represent unique risks for error and there are a variety of control processes engineered by manufacturers into POCT devices, required by accreditation agencies, or implemented by laboratories to ensure the quality of test results.
      1. Analysis of QC samples complements the control processes available for any testing device.
      2. Each test will present different risks and have unique control processes to address those risks. QC in the POC setting uses the same principles as QC in the central lab, but the practicalities of POCT QC practice are different.
      3. While POCT may seem to be relatively simple, there are many potential sources of error that need to be considered, even for waived POCT.
      4. The control plan to assure the quality of POCT must be carefully thought out with a patient focus, addressing all aspects of the testing process and potential for error throughout the pre-analytic, analytic and post-analytic phases.
      5. Automatic control processes can provide advantages but also have specific limitations over traditional QC.
      6. The ultimate control strategy for any device must balance the probability for an error to occur, ability to detect an error, and the consequences of harm to a patient should an error occur with the control processes that are available.
      7. In the real world, such control strategies must also consider staff resources and cost-effectiveness to be practical.
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