(a) Identification. An inherited nucleotide repeat disorder DNA test is a prescription in vitro diagnostic device that is intended to detect and identify the number of nucleotide repeats in a gene using genomic DNA isolated from post-natal patient specimens. It is solely intended as an aid for carrier testing and as an aid for the diagnosis of inherited nucleotide repeat-associated disorders. Assay results are solely intended to be used in conjunction with other clinical and diagnostic findings. These tests do not include those indicated for use for fetal diagnostic testing or newborn screening.

(b) Classification. Class II (special controls). The special controls for this device are:

(1) The intended use on the device's label required under § 809.10(a)(2) of this chapter and device's labeling required under § 809.10(b)(2) of this chapter must include a statement that assay results are solely intended to be used in conjunction with other clinical and diagnostic findings, consistent with professional standards of practice, and that reflex testing, clinical genetic evaluation, and genetic counseling should be offered as appropriate.

(2) The labeling required under § 809.10(b) of this chapter must include:

(i) A warning that mosaicism detected in one tissue may not reflect mosaicism in other tissues and that the significance of mosaicism should be interpreted with caution in conjunction with other laboratory and clinical information (e.g., sex of patient, diagnostic testing or carrier screening, patient symptoms) and should include appropriate genetic counseling.

(ii) A prominent statement that this test is not indicated for use for fetal diagnostic testing, newborn screening or for stand-alone diagnostic purposes.

(iii) Information that addresses how to interpret different result outputs specific to the technology, such as (peaks) in the electropherograms.

(3) Design verification and validation must include the following:

(i) Appropriate design features and control elements incorporated into the testing procedure that mitigate the risk of incorrect clinical results. These include controls as determined acceptable by FDA that:

(A) Enable the user to determine when the amplification may yield incorrect results,

(B) Enable the user to determine when cross contamination may have occurred;

(C) Software risk control measures that address device system hazards;

(D) Provide software traceability that ensures all hazards are adequately controlled and that all controls have been validated in the final device design; and

(E) Ensure the instructions for use and test reports appropriately inform the user about the limitations of the assay.

(ii) Validated and acceptable, as determined by FDA, criteria for test result interpretation and reporting, including result outputs.

(iii) Acceptable, as determined by FDA, evidence demonstrating the clinical validity of the device which supports each indicated diagnostic use, including for each genotype and associated phenotype used in providing a clinical determination for the target population.

(iv) Evidence demonstrating acceptable, as determined by FDA, analytical device performance. Patient specimens must represent the full spectrum of expected clinical results and be obtained through unbiased collection. Specimens must be representative of all categories of results and across the range of repeat sizes (e.g., categories and repeat sizes for Fragile X syndrome are: normal 1-44 repeats; intermediate 45-54 repeats; premutation 55-200 repeats, full mutation greater than 200 repeats), across a range of allelic combinations, be near decision points, and be from both male and female subjects. The number of specimens tested must be sufficient to obtain unbiased estimates of device performance. Analytical validation must include data demonstrating acceptable, as determined by FDA:

(A) Agreement with a comparator method(s) determined to be acceptable by FDA. This evidence must demonstrate the accuracy for detecting the size of the nucleotide repeats and the diagnostic categorical calls in DNA in the indicated specimen type(s) from patients that are representative of the intended use population. Accuracy must be assessed for both diagnostic and carrier subsets independently.

(B) Device precision including repeatability and reproducibility, using clinical samples. The study must evaluate all possible sources of variability including, as appropriate, between-site and between operator at a minimum of three sites of which two must be external with a minimum of two operators per site, between-day on a minimum of 3 non-consecutive days, between-run, within-run, between-lot in a minimum of three lots, and between instrument on a minimum of three instruments. Precision must be demonstrated per specimen and determine for both categorical call and by the size of the repeat (i.e., the percentage of replicates for which the allele fell within the target precision size range). Precision data must be calculated and presented with and without results determined to be invalid.

(C) Device performance at the limit of detection of each allele across the range of sizes and as a function of the indicated DNA input for the assay.

(D) Specificity of the reagents for their targets, absence of cross-reactivity, evaluation of sources of interference relevant to the specimen type, and a demonstration of the absence of cross contamination.

(E) Performance of the pre-analytical methods, including DNA extraction methods.

(F) Performance of the device across the range of indicated DNA input concentrations for the assay.

(G) Specimen stability throughout indicated specimen storage ranges, including under expected storage and transport conditions.

(v) Robust evidence demonstrating that the number and frequency of incorrect results due to mosaicism are clinically acceptable, as determined by FDA.

(vi) An appropriate traceability plan to minimize the risk of incorrect results over time, including a description of the molecular size standards and other reagents that may be required for result interpretation, as applicable, that demonstrate the reliable interpretation of the size of the fragments.

(vii) Acceptable, as determined by FDA, device stability protocols and acceptance criteria, that are sufficient to ensure indicated analytical and clinical performance throughout the indicated device stability period. The protocols and acceptance criteria must be adequate to demonstrate that there is no degradation in signal intensity of full mutations when testing a specimen at the latest indicated time point within the indicated device stability that is comprised of the lowest indicated DNA input that can be used.