Clostridioides Difficile PCR

The BD MAX Cdiff assay performed on the BD MAX System is an automated in vitro diagnostic test for the direct, qualitative detection of the Clostridioides difficile toxin B (tcdB) gene in human liquid or soft stool specimens from patients suspected of having Clostridioides difficile infection. The test, performed directly on the specimen, utilises real-time polymerase chain reaction (PCR) for the amplification of Clostridioides difficile toxin B DNA and fluorogenic target-specific hybridisation probes for the detection of the amplified DNA.

Toxigenic Clostridioides difficile Detected

Toxigenic Clostridioides difficile Not Detected

Invalid

Limitations of Test

• The BD MAX Cdiff assay is intended for use only with unpreserved liquid or soft stools; performance characteristics of other clinical specimen types have not been established.
• Erroneous test results may occur from improper specimen collection, handling or storage, technical error, sample mix-up or because the number of organisms in the specimen is below the analytical sensitivity of the test.
• A BD MAX™ Cdiff positive assay result does not necessarily indicate the presence of viable organisms. It does however indicate the presence of the tcdB gene and allows for presumptive detection of a Clostridioides difficile toxigenic organism. The BD MAX™ Cdiff assay cannot be used for species identification as it does not contain primers and probes specific to Clostridioides difficile.
• As with all PCR-based in vitro diagnostic tests, extremely low levels of target below the limit of detection of the assay may be detected, but results may not be reproducible.
• Mesalamine rectal suspension enema and Gynol II may cause slight inhibition in the BD MAX™ Cdiff assay (refer to the Interfering Substances section for further details).
• Tums and Maalox liquid may inhibit the BD MAX™ Cdiff assay (refer to the Interfering Substances section for further details).
• False negative results may occur due to loss of nucleic acid from inadequate collection, transport or storage of specimens, or due to inadequate bacterial cell lysis. The Sample Processing Control has been added to the test to aid in the identification of specimens that contain inhibitors to PCR amplification. The Sample Processing Control does not indicate if nucleic acid has been lost due to inadequate collection, transport or storage of specimens, or whether bacterial cells have been adequately lysed.
• BD MAX™ Cdiff assay results may sometimes be Unresolved due to an invalid Sample Processing Control, or be Indeterminate or Incomplete due to System failure, and require retesting that can lead to a delay in obtaining final results.
• Mutations or polymorphisms in primer- or probe-binding regions may affect detection of Clostridioides difficile tcdB gene variants, resulting in a false negative result with the BD MAX™ Cdiff assay.
• Variant toxigenic Clostridioides difficile without the tcdB gene or with a non-functional Toxin B protein are very rare.15-18 The BD MAX™ Cdiff assay targets the tcdB gene and it is unknown whether it would detect Toxin A+/Toxin B- variant strains.
• As with all in vitro diagnostic tests, positive and negative predictive values are highly dependent on prevalence. BD MAX™ Cdiff assay performance may vary depending on the prevalence and population tested.

‍