Possible disadvantages of POCT extend into the testing process. Some of these disadvantages include:
- Differences in methodology:
- POCT employs different methodologies. Limitations and interferences can vary from test methods employed in the central laboratory. Limitations include test timing and performing specific steps in the proper order. Contamination and improper sample collection are method/instrument-specific. For example, POCT glucose interference may include maltose, galactose, and xylose.
- Multiple methods for a single test. Staff may require training on multiple methods for a single test. For example, if the facility employs multiple glucose or coagulation meters, the staff must have documented training and demonstrate competency in using all methods. Test materials may not be interchanged and must be used and stored as per manufacturer's guidelines.
- Devices must be approved for single/multiple patient use. The facility must verify approved use and utilize each device only appropriately.
- Proper application of specific test methods. As the manufacturer defines, some POCT test methods must only be used for screening and cannot be used for diagnoses. Reference the package insert for proper use of a specific method/instrument. A POCT device that is used outside of the manufacturer's instructions makes the method highly complex. If the manufacturer's instructions require confirmatory testing, the specified process must be followed to maintain CLIA compliance and the assigned level of complexity.
- A test kit or device should not be used outside its intended use or the written procedure (e.g., HCG testing on serum in a waived testing setting when the package insert specifies the waived test is for urine testing only).
- Monitoring and appropriate storage of supplies and reagents: The reagent/QC storage facilities may be decentralized and in remote locations. A detailed inventory system must be integral to the POCT program to prevent deterioration, lack of stock rotation, and outdated and possibly erroneous patient results.
- Reliability of results: Variations in personnel, testing conditions and methods, and perceived simplicity of testing methods all contribute to the potential lack of reliability.
- Personnel: Variations in educational and experience levels of staff performing the tests and potential staff turnover can impact the reliability of results.
- Test result variability: Compared to central laboratory testing, POCT may experience more significant test result variability.
- Simplicity of waived testing is deceptive: Incorrect results can be generated when all variables are considered. Staff training and monitoring with appropriate competency assessment will reduce the error level.
- Test results may not be comparable to central laboratory results: POCT methods differ from those employed in the central laboratory. Comparison of results or standardization across POCT sites or locations may not be possible. This variability may impact patient care.
- Patient outcome: POCT does not guarantee improved patient outcomes. POCT provides test results with a faster turnaround time in most instances. To effectively expedite clinical management, the entire clinical pathway must be optimized. A faster test result can contribute to improved patient outcomes but does not provide the sole factor for this final analysis
