cobas® liat system support: Troubleshooting

An invalid is generated when abnormalities in PCR amplification of the internal processing control or assay targets are detected. Invalid results can be expected to occur at a low rate when PCR conditions are not optimal. 

For specific information on invalid failure codes, refer to the Failure Codes chart of the relevant cobas® liat assay’s method sheet. These detailed charts provide information on the various failure codes for each specific cobas® liat assay.

Best practices to minimize invalid results

To reduce the rate of invalid results, follow these best practices:

• Perform specimen collection using only the recommended swab types. DO NOT use cotton or calcium alginate swabs, or swabs with wood shafts. Inadequate or inappropriate sample collection, storage, and transport may yield incorrect or invalid test results. 
• Only use the collection materials indicated in the method sheets as they have been validated or approved for use with the cobas® liat system. Inappropriate sample media composition or volume may impact test results. 
• Use only the transfer pipettes contained in the Assay and Quality Control Kits. Invalid results may be obtained if there is insufficient sample volume. The use of alternative transfer pipettes may lead to invalid results. 
• Be aware that interfering substances, such as blood and mucus, may prevent nucleic acid target extraction and/or amplification and detection, leading to invalid results. The Internal Processing Control is included to help identify the specimens containing substances that may interfere with nucleic acid isolation and PCR amplification.

Troubleshooting assay invalids

If you receive an invalid result, repeat the assay with the same patient specimen. If an additional invalid result is generated, do not continue testing that patient specimen. Instead, collect a new specimen from the patient and repeat the assay using the new specimen. If sample recollection is not available, or if the invalid result persists, you might consider sending the sample to a laboratory for confirmatory testing.

If you are experiencing an increased rate of invalids, contact Roche cobas® liat system Technical Support at 1-800-800-5973 for additional assistance troubleshooting.

An assay abort is the premature termination of a sample test. Assay aborts are designed to prevent excessive movements during operation that could result in analyzer damage. Occasional assay aborts are a normal and expected result of this important failsafe. Under normal operation, the analyzer alerts the user if a malfunction or error is detected.

Troubleshooting assay aborts

When you receive an assay abort, follow the steps below:

1. Confirm the assay abort and reboot the analyzer. You must reboot the analyzer after each assay abort. The analyzer performs self-diagnostics during startup (initialization). If the initialization does not complete successfully, contact Roche cobas® liat system Technical Support at 1-800-800-5973.
2. If the initialization completes successfully without error, repeat the assay again.
3. If the issue persists, or you are experiencing an increased rate of aborts, please contact Roche cobas® liat system Technical Support at 1-800-800-5973 for additional assistance troubleshooting.