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. Refer to the package insert for proper use of a specific method/instrument. A POCT device used outside 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).
