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Molecular Diagnostics

Next-Generation Sequencing (NGS)

Next-Generation Sequencing (NGS) is a Molecular Diagnostics laboratory test reference in the LabPedia Medical Laboratory Library. Massively parallel sequencing of gene panels, exomes, genomes, or transcriptomes; cornerstone of modern germline and somatic molecular diagnostics.

Also known asMassively parallel sequencing; MPS; Deep sequencing

Overview

NGS simultaneously sequences millions of DNA (or cDNA) fragments, enabling broad variant detection across panels or larger targets after bioinformatic analysis.

Clinical Importance

Multi-gene germline disease panels and carrier screening

Somatic tumor profiling for therapy selection

Specimen Requirements

  • Specimen: assay-validated specimen type (blood, swab, tissue, fluid, or other as ordered)
  • Collection: use the manufacturer-/SOP-specified collection device and preservative
  • Handling: avoid contamination with extraneous nucleic acid; change gloves between specimens
  • Transport: follow temperature and time limits for RNA (more labile) vs DNA targets
  • Stability: do not exceed validated storage limits; freeze–thaw cycles may reduce yield
  • Germline: EDTA blood common; tumor: FFPE/tissue with adequate neoplastic content

Analytical Method

Libraries are prepared (fragmentation, adapters, target enrichment for panels), sequenced on short-read (or other) platforms, then aligned and variant-called. Clinical reports include coverage metrics, limitations, and classified variants per ACMG/AMP or somatic guidelines.

Instruments Used

Automated analyzers

  • Illumina sequencing platforms
  • Thermo Fisher Ion Torrent platforms
  • Automated library preparation systems

Manual methods

  • Manual library prep with instrument sequencing and pipeline analysis

Reference Values

Molecular cutoffs, units (IU/mL, copies/mL, Ct), reportable ranges, and variant classifications are assay- and laboratory-specific. Always interpret against the performing laboratory report, manufacturer IFU, and current CLSI / CAP / AMP / ACMG guidance as adopted locally. Limit of detection and inhibition controls are essential for negative results.

No single reference interval. Reportable variants depend on validated genes, coverage depth, and classification frameworks. VUS rates vary by panel and ancestry representation.

Interpretation

Common Causes of Increased Results

  • Pathogenic/likely pathogenic or actionable somatic variants; interpret with clinical context and guidelines

Common Causes of Decreased Results

  • No reportable variant in covered regions; does not exclude disease genes/regions outside the assay

Clinical Significance

  • Inherited disease diagnosis
  • Oncology targeted therapy panels
  • Carrier and pharmacogenomic panels when designed for those indications

Factors Affecting Results

Pre-analytical

  • Wrong specimen type or transport medium for the validated assay
  • Delayed transport degrading RNA targets
  • Contamination during collection (especially amplicon-rich environments)
  • Inadequate volume or low cellularity/tumor content
  • Low tumor purity reducing somatic variant detection

Analytical

  • Pipeline version changes affecting calls
  • Homopolymer and pseudogene challenges (platform-dependent)

Post-analytical

  • Over-interpreting VUS as diagnostic

Advantages and Limitations

Advantages

  • Broad content
  • Detects multiple variant types when validated

Limitations

  • Does not replace all methods (e.g., some structural variants need orthogonal tests)
  • Requires robust bioinformatics and interpretation expertise

Clinical Pearls

NGS is only as clinical as its validated gene list and coverage; a negative panel is not a negative genome.

Related Laboratory Tests

References

Authoritative textbooks, guidelines, and reviews supporting this laboratory test reference. Verify reference intervals, critical limits, and method details against institutional protocols and current guideline editions.

Textbooks

  • McPherson RA, Pincus MR. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Elsevier; 2021. (Molecular diagnostics chapters, verify current edition.)
  • Buckingham L. Molecular Diagnostics: Fundamentals, Methods, and Clinical Applications. 3rd ed. F.A. Davis; 2019. (Verify current edition and institutional adoption.)

CLSI and Professional Guidelines

  • Clinical and Laboratory Standards Institute (CLSI). Consult current CLSI molecular method documents available through your laboratory, document numbers and editions change; do not treat any single CLSI title as universal.
  • Institutional molecular laboratory standard operating procedures (SOPs), assay manufacturer instructions for use (IFU), and locally adopted accreditation requirements. Always verify current local practice.
  • Clinical and Laboratory Standards Institute (CLSI). Molecular method evaluation and related documents (verify current CLSI editions applicable to the assay).
  • College of American Pathologists. Molecular pathology accreditation and proficiency testing expectations (verify current CAP checklist requirements).
  • Association for Molecular Pathology (AMP). Practice guidelines and position statements for molecular diagnostics (verify current AMP documents for the assay).
  • American College of Medical Genetics and Genomics (ACMG). Standards and guidelines for interpretation of sequence variants and related genetic testing practice (verify current ACMG documents).

WHO Publications

  • World Health Organization. Laboratory and diagnostic guidance relevant to molecular testing (verify current WHO publication for the assay/pathogen).

Frequently Asked Questions

Common questions about using this Next-Generation Sequencing (NGS) laboratory test Medical Laboratory Library reference in Medical Laboratory Science education.

What is the Next-Generation Sequencing (NGS) laboratory test reference used for?

This Medical Laboratory Library page summarizes the clinical importance of Next-Generation Sequencing (NGS). Review the Clinical Importance section for why the test is ordered in laboratory medicine practice.

Where can I find Next-Generation Sequencing (NGS) specimen requirements?

See the Specimen Requirements section on this page for specimen information related to Next-Generation Sequencing (NGS). Confirm collection details against your laboratory protocol.

Where are Next-Generation Sequencing (NGS) reference values listed?

See the Reference Values section on this Laboratory Library page. Reference ranges can vary by method and population, so verify intervals with your laboratory.

How do I interpret Next-Generation Sequencing (NGS) results?

Use the Interpretation section for laboratory interpretation framing, including increased and decreased result patterns when provided. Do not treat educational text as a patient-specific diagnosis.

What analytical method is used for Next-Generation Sequencing (NGS)?

See the Analytical Method section for principle and method notes. Method details may differ by instrument and institutional SOP.

Are related laboratory tests linked from Next-Generation Sequencing (NGS)?

Yes. The Related Laboratory Tests section lists connected references for continued lookup in the Medical Laboratory Library.

How can I continue learning after reading Next-Generation Sequencing (NGS)?

Use Continue learning links on this page for related Academy lessons, medical laboratory quizzes, or laboratory case studies when available for this Molecular Diagnostics topic.

What are the clinical pearls for Next-Generation Sequencing (NGS)?

See the Clinical Pearls section for concise laboratory practice notes associated with Next-Generation Sequencing (NGS). Apply pearls alongside institutional protocols.

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