Product FAQs

GENERAL INTERFERENCE TESTING QUESTIONS

Q: Are there regulations that require me to perform interference testing in my laboratory?

A: Manufacturers are required to perform interference testing on their assays and include this information in the package insert. For most laboratories, relying on the manufacturer’s claims is considered sufficient to meet regulatory requirements. However, the laboratory director may wish to verify manufacturer’s claims, especially if information regarding the experiments and results is not comprehensive.

Q: Are there guidelines for performing interference testing experiments, including analyte concentrations?

A: Yes! The Clinical and Laboratory Standards Institute (CLSI) has approved a guidance document on interference testing: CLSI, INTERFERENCE TESTING IN CLINICAL CHEMISTRY; APPROVED GUIDELINE, 2ND ED, CLSI DOCUMENT EP07-A2, WAYNE, PA, 2005.

Q: What are some of the most common interferents?

A: Interference from hemolysis (hemoglobin and /or red blood cell contents), lipemia (triglyceride-rich lipoproteins and turbidity), icterus (unconjugated or conjugated bilirubin), and proteins (albumin and gamma-globulins, paraproteins) are so common with routine chemistry assays, that validation by manufacturers always includes interference testing for these substances.

Q: What type of material is used to perform interference testing?

A: The EP7-A guidance document outlines materials that can be used to perform interference testing. However, many of the materials are difficult to obtain. Additionally, labs may store abnormal patient samples that fit their needs or use artificial interferent substitutes. For example, lipema is often simulated using IntraLipid®. Unfortunately, the photometric response to this synthetic “fat” differs from physiological lipema and is inappropriate for interference studies.

ASSURANCE INT-01 PRODUCT QUESTIONS

Q: What interferents are included in the ASSURANCE™ Interference Test Kit INT-01?

A: The interferents include:

  • Human triglyceride-rich lipoproteins for evaluation of lipemia interference;
  • Human hemolysate for evaluation of hemolysis interference;
  • A mixture of human serum albumin and gamma-globulins to evaluate protein interference;
  • Conjugated and unconjugated bilirubin to evaluate interference from icterus.

Q: What preservatives are added to the materials?

A: We do not add any stabilizers or preservatives to the interferents. The materials are either human-sourced or purified chemicals that are highly concentrated (up to 20X the CLSI recommendation).

Q: How will ASSURANCE benefit my laboratory?

A: With the availability of a kit, interference testing becomes more practical. Laboratories no longer need to find patient samples that fit their needs, store untested patient samples, or obtain artificial interferent substitutes, such as IntraLipid®. ASSURANCE™ contains stable, highly concentrated, human-sourced and/or purified materials that are representative of actual interferents encountered during testing. The human-sourced material is tested and found negative/non-reactive for infectious disease. The recommended testing protocols and data analysis tools can be worked into the laboratory procedure for interference testing, helping lab directors and managers ensure that their assay results are reliable. ASSURANCE™ Interference Test Kit from Sun Diagnostics will simplify interference testing.

ASSURANCE TECH SUPPORT FAQs

Q: How do I perform interference testing?

A: The Clinical and Laboratory Standards Institute (CLSI) has approved a guidance document on interference testing: CLSI, INTERFERENCE TESTING IN CLINICAL CHEMISTRY; APPROVED GUIDELINE, 2ND ED, CLSI DOCUMENT EP07-A2, WAYNE, PA, 2005. Sun Diagnostics has created a recommended testing protocol based on CLSI EP7-A guidelines. This protocol is available for download here.

Q: How do I analyze and interpret the data generated from my interference studies?

A: Sun Diagnostics has created a data analysis tool based on CLSI EP7-A guidelines. This tool is available for download here.

Q: How do I know the actual concentrations of the interferents in the kit?

A: As discussed in the testing protocol, we recommend that you assay the materials prior to beginning your experiments. This will provide information on how the materials are responding on your specific analyzer. If it isn’t feasible to assay the materials, you can use the “typical values” provided in the package insert as a guide. For more information, contact Sun Diagnostics Tech Support via email support@sundiagnostics.us or via phone 1-877-SUN-DIAG (877-786-3424)

GENERAL PRECIPITATION REAGENT QUESTIONS

Q: What are the traditional approaches to precipitating lipoproteins? What are their drawbacks?

A: Traditional approaches include chemical precipitation, which may not completely remove apo-B containing lipoproteins; electrophoresis and/or ultracentrifugation, which are labor intensive, technically demanding, and may alter particle composition and structure.

Q: Is there another way to precipitate lipoproteins?

A: Immunoprecipitation, using monospecific antibodies directed towards lipoproteins, is the most specific method available for the separation of lipoproteins.

LIPOSEP IP QUESTIONS

Q: What are some benefits to LipoSep IP™?

A: LipoSep IP™:

  • Is a highly specific tool to isolate HDL in serum, allowing for HDL-C measurement using a Total Cholesterol assay. TCHOL assays are less expensive, more standardized, and more accurate than homogeneous HDL-C assays.
  • Has a simple, straightforward procedure
  • Does not alter lipoprotein particle composition
  • Other HDL components, such as apo AI, apo E, and myeloperoxidase can also be measured.

Q: How does immunoprecipitaiton with LipoSep IP compare to chemical precipitation with dextran sulfate?

A: Results are comparable between the two methods, with LipoSep IP being more robust and able to precipitate higher levels of triglyceride-rich lipoproteins. Please download a copy of the poster presented at AACC 2013 for more information.