Frequently Asked Questions
Q) How does Liquid Crystal technology work?
A) The CDx technology is based on antibody‐microbe aggregates reaching sufficient size (called the critical diameter) to distort a Liquid Crystal matrix, which results in an amplified detectable signal.
Q) Is Liquid Crystal dangerous or toxic?
A) The Liquid Crystal used by CDx is not toxic nor dangerous.
Q) Why must the Liquid Crystal be heated for at least 20 minutes prior to starting the diagnostics? What should I do if particles are visible in the Liquid Crystal?
A) The Liquid Crystal requires as long as 20 minutes to completely transition to the liquid phase from its lyophilized state. Using incompletely dissolved Liquid Crystal will result in increased background during diagnostics and may result in an inaccurate test. If particles are still present after 20 minutes, the temperature should be checked to make sure the heating block is at 60 – 65 °C. If particles persist after additional heating, the Liquid Crystal should be discarded, and new product rehydrated.
Q) Can the Liquid Crystal be prepared ahead of time?
A) Liquid Crystal can be rehydrated at the beginning of the test day as long as the stoppered vial remains at the proper temperature.
Q) Is the BioCassette reusable?
A) The BioCassette is NOT reusable and should be discarded using appropriate laboratory methods for enriched sample disposal.
Process and Samples
Q) What is the purpose of the negative control and why is one needed for every sample?
A) The negative control is utilized as a baseline for microsphere concentration (in comparison to the concentration of antibody conjugated microspheres) and is also an indicator of overall sample microflora concentration.
Q) What are the chances of cross contamination?
A) Because the CDx System is not PCR based and does not replicate the target during testing, the chances of cross contamination are virtually non‐existent.
Q) Can the antibodies be prepared ahead of time?
A) The antibodies are supplied in two forms: liquid or lyophilized. Lyophilized antibodies can be rehydrated up to 1 hour before the samples complete enrichment as long as they remain in the rehydration buffer. If antibodies are purchased in the liquid form, they should be well mixed, aliquoted to the appropriate samples, and the remaining unused contents returned to the refrigerator.
Q) How long can the enriched samples and final microsphere samples be stored?
A) Enriched samples can be saved for additional confirmation testing, but we do not recommend storage and retesting using the CDx System. Final microsphere samples (post immunomagnetic separation) can be stored at room temperature and tested for up to 1.5 hours following immunomagnetic separation.
Q) Can the samples be enriched longer than the enrichment period stated in the protocol?
A) The time of enrichment is designed to maximize target bacteria and minimize background microflora. The samples should be enriched according to the specified time in the protocol, and varying treatments have been developed for different assays. Please see the package insert for processing treatments for different enrichment times.
Q) Are particulates and foreign matter in the system a problem?
A) Particulates exceeding the critical diameter would distort the Liquid Crystal matrix resulting in a non‐specific detectable event. The CDx protocols are designed to eliminate non‐specific aggregates.
Q) What happens if the components of the test are not fully warmed prior to the diagnostics?
A) Increased background in the test can occur and results may not be accurate.
Q) What is the limit of detection (LOD) of the system?
A) The current system LOD is 10^4 cfu/ml to 2 × 10^5 depending on the assay. Therefore, a minimum of nine hours of enrichment is required to detect 1 cfu per sample, and may require more time depending on the assay.
Q) What is the False Positive rate?
A) In an independent lab test, the false positive rate was determined to be less than 1% in raw ground beef.
Q) Why does the CDx system need less enrichment time than most other comparable methods?
A) Less enrichment time is needed because the use of selective antibodies concentrates the pathogenic bacteria and sample processing reduces unwanted materials, which results in an increased signal to noise ratio.
Q) What other tests are being developed for the CDx System?
A) Testing for Campylobacter ssp., specific Salmonella serovars, Cannabis pathogens and toxins, and biothreat agents are currently in development.
Q) Immunoassays are known to have cross‐reactivity with other bacteria; what makes the CDx System unique?
A) The CDx System combines high affinity antibodies, robust immunomagnetic separation, and amplification of the signal using Liquid Crystal to reduce the effects of cross reactivity and increase sensitivity of true positive samples.
Q) Why should the reader be turned off after use?
A) After running the test, the reader should remain on for approximately 4 hours while all files are downloaded and emails sent. At that time, the reader should be powered off to avoid moisture accumulation in the unit.