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U.S. Department of Health and Human Services
Food and Drug Administration
Center for Devices and Radiological Health
Division of Chemistry and Toxicology Devices
Office of In Vitro Diagnostics Evaluation and Safety
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Labeling for in vitro diagnostic devices must satisfy the requirements found in 21 CFR 809.10. Specific recommendations for zonisamide and lamotrigine assays, regarding some of these requirements, are described below.
Specimen collection and storage:
You must include instructions for specimen collection and preparation for analysis. 21 CFR 809.10(b)(7). We recommend that you include the following:
- Discussion of any limitations or instructions related to the specimen type, including the appropriate matrix, anticoagulants, preservatives, or collection tubes.
- Instructions concerning preserving integrity of the specimen, such as required temperatures or materials for collection, transport, storage (short and long term), and assay procedural steps. Storage conditions that you recommend to the user should be based on the conditions you have validated for your test system. You should clearly define acceptance criteria that you apply (e.g., x% recovery) in determining the recommended storage conditions. Information on storage conditions based on literature can be cited if it is applicable to your test system.
- Discussion of the importance of consistency and accurate recording of time of blood draw with respect to the last dose if this is relevant for interpretation of results.
You must provide a step by step outline of recommended procedures from reception of the specimen to obtaining results. 21 CFR 809.10(b)(8). We recommend that you include the following as part of the procedure:
- A validated procedure for dilution, if you instruct users to dilute samples with values above the highest calibrator.
- Steps, based on procedures you have validated for your test system, that users can take to minimize the effect of carryover or other causes of bias or imprecision.
- Any special handling instructions for reagents.
Quality control and calibration procedures
The step by step outline of the procedure must include details of kinds of quality control procedures and materials required, as well as details of calibration. 21 CFR 809.10(b)(8)(v) and 21 CFR 809.10(b)(8)(vi). You should advise users of the specifics of calibration and quality control procedures necessary to ensure your stated performance claims. We recommend that you include a statement in your package insert that laboratories should follow federal, state, and laboratory guidelines for quality control. When you specify ranges for your quality control material, you should clarify how these were determined and indicate that laboratories should determine their own acceptable ranges based on their own acceptance criteria. We also recommend that you identify the material to which your calibrator is traceable. If you do not market these materials for your assay, you should include recommendations for appropriate quality control materials.
If your 510(k) includes calibrator or control materials to be sold separately from your assay, you should include the separate labeling for these components.
Warnings and Precautions
When blood products are used as components, you should include a statement in your package insert that the animal/human source components containing any blood-product derived material has been tested by FDA approved (or equivalently recognized) assays and found to be negative for HIV type 1 (HIV-1) and type 2 (HIV-2), as well as for hepatitis B surface antigen and antibody to hepatitis C virus (HCV), and found to be negative (not repeatedly reactive). You should also clarify that, because no testing can offer complete assurance that these or other infectious agents are absent, this material should be handled using good laboratory practice to avoid skin contact and ingestion.
You must include a statement of limitations of the procedure. 21 CFR 809.10(b)(10). You should identify any factors known to affect results and describe the effect on results (e.g., highly lipemic samples may cause falsely low results).
It may be appropriate in some cases to recommend that it is generally good practice to use the same assay and matrix consistently for individual patients.
You must indicate how reference ranges were established, including identifying the population on which it was established. 21 CFR 809.10(b)(11). At this time, we recommend, that you state that therapeutic ranges are not well-established for zonisamide and lamotrigine and include explanations such as the following:
Considerable overlap has been observed between serum levels in responders and non-responders as well as between levels associated with seizures and adverse effects, and there is not a clear relationship between lamotrigine serum concentration and clinical response across patients. Optimal ranges may vary among patients. Caution should always be exercised regarding individual patient management based upon observed reference ranges; assay results should always be interpreted in combination with careful observation of clinical response.
We recommend that, rather than citing a reference range based on a single study, you cite and summarize balanced and representative studies in the literature concerning serum concentration ranges that have been observed in those studies to be associated with seizure control or with adverse effects. When summarizing studies, we recommend that you include relevant points, such as the sampling time (relative to time of drug dose), the assay methodology, and the nature of the population tested in that study (e.g., newly diagnosed). If studies have shown lack of correlation, we recommend you discuss this as well. We ask that you include in your 510(k) copies of references you use to support statements concerning ranges cited in your labeling. You should clarify that reference ranges should only imply a lower limit below which therapeutic response is relatively unlikely and an upper limit above which toxicity is relatively likely to occur in the specific populations studied. Clinicians using proposed ranges should be aware that because of individual variation some patients may achieve therapeutic benefit with serum drug concentrations outside the range or may experience toxicity with levels below the lower limit of the reference range.
We recommend that you refer to the drug package insert regarding pertinent pharmacokinetic information including: time to steady state, appropriate sample draw times (with respect to dose), and clinical conditions or co-administered drugs that may affect pharmacokinetics.
You should discuss, or refer to the drug label, regarding information such as time to steady-state, or recommended sampling times.
You must include specific performance characteristics of the assay. 21 CFR 809.10(b)(12). We recommend that you summarize the study design and results for each performance characteristic discussed in Section 6. Your representation of study designs and results in the package insert should include information relevant to aid the user in understanding test performance. The reportable range claimed in the package insert should be based on the assay range for which you have validated precision, linearity, and method comparison. The CLSI guidelines, referred to in Section 6 – Performance Characteristics, include instructions and examples for statements of claims in the labeling. We recommend you follow these formats in your labeling. You should include data plots of the method comparison study. If your assay is for use with more than one instrument, you should specify in the package insert the instrument used to evaluate the performance characteristics represented in the package insert.
1 FDA docket: FDA-2004-D-0421.
2 Guidances specifically for sirolimus, cyclosporine and tacrolimus assays are available at http://www.fda.gov/MedicalDevices/DeviceRegulationandGuidance/GuidanceDocuments/ucm077267.htm, and http://www.fda.gov/MedicalDevices/DeviceRegulationandGuidance/GuidanceDocuments/ucm092778.htm. These guidances address additional issues including sample pre-treatment for whole blood samples and cross-reactivities for immunosuppressant assays.
3 We recommend that you contact OIVD for feedback regarding possible regulatory routes and validation strategies if you are considering submitting premarket submissions for new types of assays.
4 Patsalos et al, “Antiepileptic drugs–best practice guidelines for therapeutic drug monitoring: a position paper by the subcommission on therapeutic drug monitoring, ILAE Commission on Therapeutic Strategies.” Epilepsia 49 (2008)1239-76.
5 The current labeling for lamotrigine states “the value of monitoring plasma concentrations of LAMICTAL has not been established. Because of the possible pharmacokinetic interactions between LAMICTAL and other drugs including AEDs, monitoring of the plasma levels of LAMICTAL and concomitant drugs may be indicated, particularly during dosage adjustments. In general, clinical judgment should be exercised regarding monitoring of plasma levels of LAMICTAL and other drugs whether or not dosage adjustments are necessary.”
6 In this context, the term “reference material” refers to material whose properties are sufficiently homogeneous, stable and well established to be used for the calibration of a measuring system, the assessment of a measurement procedure, or for assigning values to materials.
7 Preparation of sample dilutions by consecutive 1:1 dilutions of a high sample may not be sufficiently well-distributed throughout the assay range, especially near the lower end of the assay range; therefore we do not recommend this approach. In addition, we do not recommend the approach of preparing multiple dilution series’, each spanning only part of the assay range.
8 For testing collection tubes/anticoagulants, see Section 6G-Matrix Comparison.
9 We do not recommend selecting multiple samples from a small number of patients in order to achieve the adequate sample size since this may not evaluate the effect of inter-individual variability.
10 Additional FDA guidance documents generally addressing calibrators and controls include “Abbreviated 510(k) Submissions for In Vitro Diagnostic Calibrators; Final Guidance for Industry” ucm092800 and “Assayed and Unassayed Quality Control Material”.ucm079179
11 The term accuracy in this context is related to both trueness and precision of measurement.
12 See International Standards Organization, 2003 “Metrological Traceability of Values Assigned to Calibrator and Control Materials,” ISO Document 17511.