NGS Assay Validation Under CLIA
Most clinical NGS tests are laboratory-developed or modified, so CLIA requires the lab to establish, not just verify, performance specifications before reporting patient results.
SLC is an independent, nationwide clinical laboratory consulting network. We are not affiliated with, authorized by or endorsed by any sequencing platform maker, kit supplier or accrediting organization.
Regulatory basis
42 CFR 493.1253(b)(2) applies to tests the lab develops, modifies, or that are not subject to FDA clearance. The lab must establish accuracy, precision, analytical sensitivity, analytical specificity including interfering substances, reportable range, reference intervals, and any other required performance characteristic, plus calibration and control procedures.
Design the study
Define intended use, specimen types, target regions and variant classes. Select reference materials such as well-characterized cell lines and genome-in-a-bottle reference samples, previously tested clinical samples and contrived samples. Professional guidelines (AMP/CAP joint recommendations, CLSI MM09) describe statistical approaches to sample numbers.
Accuracy
Compare results with an orthogonal method or reference truth set, by variant type. Report positive percent agreement and positive predictive value with confidence intervals.
Precision
Repeatability (same run) and reproducibility (different runs, operators, days, instruments, reagent lots).
Analytical sensitivity / LoD
For somatic assays, use dilution series to find the lowest variant allele fraction detected reliably; for all assays, define minimum coverage and input.
Analytical specificity
Assess false positives, homologous regions and pseudogenes, and interferents and specimen quality issues.
Reportable range
Define the regions, variant types and sizes the test reliably reports, and document regions excluded for low coverage.
Bioinformatics
Validate the full pipeline end to end with locked versions. Changes later require documented revalidation. See pipeline validation.
Validation report
Summarize data, acceptance criteria, deviations, and limitations; the laboratory director signs before go-live.
Sample sets in practice
A practical validation set combines reference materials with known variants, previously tested clinical samples with orthogonal results, and samples representing each specimen type and quality level you will accept, such as FFPE blocks of different ages. Include variants in difficult regions and at the edges of your claims, such as the lowest allele fraction or largest indel you plan to report.
Acceptance criteria before data
Write acceptance criteria into the validation plan before testing, for example minimum sensitivity and positive predictive value by variant type with confidence intervals, and precision agreement targets. Defining criteria after seeing results is a common inspection finding.
Specimen types and preanalytic variables
Validate each specimen type you accept, such as blood, saliva, FFPE tissue or bone marrow, and define limits for input amount, fixation and age. If you plan to accept specimens outside these limits with a disclaimer, test that scenario too.
Confirmatory testing policy
Decide whether some variant types or quality levels require orthogonal confirmation before reporting, based on validation data. Document the policy and its rationale.
Verification of FDA-approved NGS tests
If you use an FDA-approved NGS test system without modification, 42 CFR 493.1253(b)(1) requires verification of accuracy, precision and reportable range and confirmation of reference intervals rather than full establishment. Any change to the approved workflow, specimen type or software turns it into a modified test requiring validation.
How SLC helps
SLC designs validation plans, helps assemble sample sets, analyzes data, drafts the validation report for director review and builds the SOPs and QC criteria that follow. Plans from $500.
Reportable range for NGS
For sequencing, reportable range means the genomic regions, variant types and size limits the test can reliably report. Define it from validation data: list covered regions meeting your minimum coverage, document regions excluded or reported with limitations, and state the largest insertion or deletion size and the copy number events detected. Put these limits on the report or in the test directory.
Reference intervals
Most NGS tests are qualitative and do not use classic reference intervals, but you still need to define what a normal or negative result means, such as no reportable variants detected in the assessed regions.
Precision study design
Choose samples with a range of variants and run them in replicate within a run (repeatability) and across runs on different days, by different operators, and on different instruments or reagent lots if you will use more than one (reproducibility). Measure concordance of variant calls and of key quantitative values such as variant allele fraction.
Limit of detection study
For somatic tests, prepare dilution series of samples with known variants into wild-type background, test multiple replicates at each level, and define LoD as the lowest allele fraction detected reliably at your chosen rate. Combine with minimum coverage requirements, because detection depends on depth.
Analytical specificity in sequencing
Analytical specificity covers false positive calls and interference. Test homologous genes and pseudogenes that can mis-map reads, regions with high or low GC content, and specimens with potential interferents such as heparin, hemolysis or excess formalin fixation. Review every false positive in the validation set and describe how filters or confirmation address it.
After validation: ongoing verification
Validation is a snapshot. After go-live, ongoing QC, PT or alternative assessment, discrepancy tracking and periodic review show the test still performs as validated. Review the validation summary whenever you plan a change, and record whether the change needs new data.
Common validation findings
Validation plan written after data collection
Too few variants of a claimed type, such as CNVs or large indels
Different pipeline version used clinically than in validation
Specimen types reported that were never validated
No director signature or date before patient testing
Software: compliance tracking with myLabCompliance
Paper binders and spreadsheets break down once a lab runs multiple instruments, shifts and testing personnel. We recommend myLabCompliance, a web-based CLIA compliance management platform for technical consultants, lab directors, lab owners and quality teams. Its public site describes tools for personnel management, validation, quality control, equipment, document control, scheduling, analytics and audit-ready workflows.
QC logs and quality control records kept in one place
Personnel records and competency tracking
Validation records for new instruments and methods
Equipment records for maintenance and calibration
Document control for SOPs and policies
Scheduling for recurring tasks such as PT events and competency
More NGS resources from SLC
Frequently asked questions
What is the difference between verification and validation?
Verification confirms an FDA-cleared test meets the maker's claims; validation establishes performance for LDTs and modified tests.
Who signs the NGS validation?
The laboratory director.
Does the bioinformatics pipeline need validation?
Yes; it is part of the test system.
Sound Lab Consultants (SLC), PO Box 2135, Chandler, AZ 85244. A nationwide clinical laboratory consulting network. Plans from $500.