Comparative Genomic Hybridisation (CGH) technology has transformed the way genetic screenings generate and interpret chromosomal data. CGH technology provides high-resolution genetic data that may reveal chromosomal imbalances at a level of detail that goes beyond what conventional methods such as standard karyotyping can typically detect. For individuals exploring private genetic screening options in London, understanding what this technology does — and what it can meaningfully highlight — is an important first step.
What Is CGH Technology? A Clear Definition
Comparative Genomic Hybridisation (CGH) is a molecular cytogenetic technique used to detect copy number variations (CNVs) across the entire genome. In simple terms, it compares a patient's DNA against a reference genome to identify regions where chromosomal material may be duplicated or deleted.
> Snippet Definition (40–50 words): CGH technology is a genomic analysis method that compares an individual's DNA to a reference sample to detect chromosomal gains or losses. Array CGH, the high-resolution version, can identify submicroscopic imbalances across the entire genome simultaneously, offering significantly greater detail than traditional karyotyping approaches.
Array CGH — the most widely used modern form — uses a microarray chip containing thousands of DNA probes, allowing simultaneous analysis across all chromosomes. This approach can detect abnormalities at a resolution many times finer than a standard chromosome analysis.
Practical Insight: Array CGH may highlight chromosomal copy number variants that conventional blood testing or standard chromosome analysis might not capture, making it a valuable tool in comprehensive genetic screening panels.
How Does CGH Technology Work? (Step-by-Step Overview)
Understanding the process can help demystify what happens when a genetic sample is submitted for CGH-based analysis.
Practical Insight: The entire analytical process is laboratory-based and generates quantitative data. The interpretation of results — particularly distinguishing clinically significant findings from benign variants — requires careful, expert review by a qualified genetics professional.
CGH vs. Traditional Chromosome Analysis: A Comparison
Understanding where CGH sits relative to other genetic testing methods helps clarify when it may be the appropriate choice.
| Feature | Standard Karyotyping | FISH Testing | Array CGH |
|---|---|---|---|
| Resolution | ~5–10 Mb | Targeted regions only | ~50–200 Kb or finer |
| Genome Coverage | Whole genome (low resolution) | Specific loci only | Whole genome (high resolution) |
| Detection of CNVs | Limited | Limited | Comprehensive |
| Detects Balanced Rearrangements | Yes | Limited | No |
| Turnaround Time | 2–4 weeks | 3–7 days | 7–14 days (approx.) |
| Clinical Use | Broad chromosomal overview | Targeted deletion/duplication | Detailed CNV profiling |
Mb = Megabase; Kb = Kilobase. Resolution values are approximate and may vary by laboratory platform.
Practical Insight: Array CGH is particularly well-suited when a higher level of genomic detail is required. It does not, however, detect all types of genetic changes — for example, balanced translocations or single-gene mutations are not typically identified through this method alone.
What Can CGH Genetic Screening Data Potentially Reveal?
CGH-based genetic screening can generate data that may suggest the presence of chromosomal copy number variants (CNVs) associated with a range of conditions. These can include:
It is important to note that not all detected variants are clinically significant. Some CNVs are classified as variants of uncertain significance (VUS), meaning their impact on health is not yet fully understood. Results should always be reviewed and contextualised by an appropriately qualified professional.
Practical Insight: A CGH report alone does not constitute a diagnosis. It provides a detailed genomic dataset that can support further clinical assessment when interpreted alongside personal and family history.
Who May Benefit from CGH-Based Genetic Screening?
CGH genetic screening may be considered relevant for a range of individuals, including:
This list is educational and does not constitute clinical advice. Any decision to pursue genetic screening should be made in discussion with an appropriate healthcare professional.
How Often Should Genetic Screening Be Considered?
Unlike routine blood tests, CGH genetic screening is not typically a recurring annual test. In most contexts:
Practical Insight: CGH genetic screening is most meaningful when pursued with a clear purpose. Speaking with a qualified healthcare professional before booking can help ensure the right test is selected for your specific circumstances.
Understanding Your CGH Results
Receiving genetic screening results can raise questions. Here is a general guide to how CGH reports are typically structured:
Understanding which category applies to any finding is essential. Genetic counselling — available through NHS clinical genetics services or independent providers — is strongly recommended following any CGH result that requires interpretation.
Practical Insight: A detailed written report accompanies all laboratory-based CGH results. This report will typically include the genomic coordinates, estimated size, and database references for any flagged variants.
Private Genetic Screening in London: What to Expect
London offers a growing range of private testing services for individuals who prefer to access health screening outside the NHS pathway. At Private Blood Tests London, we are a nurse-led clinic providing professional sample collection, screening coordination, and results reporting — without the waiting times often associated with standard referral pathways.
Our service is testing and reporting only. We do not offer prescriptions, treatments, or specialist medical consultations. We work to ensure that all samples are processed by accredited laboratories and that results are communicated clearly, accurately, and in line with UK regulatory standards.
If you are considering a broader health review, you may also find it helpful to explore our health screening packages or review our range of private blood tests available in London. For those considering reproductive health screening, our female hormone blood tests may also be relevant as part of a broader assessment approach.
Additionally, individuals with questions about broader genetic health markers may find our comprehensive blood test panels a useful starting point for general health awareness.
Practical Insight: Accessing private screening in London can offer faster results and greater scheduling flexibility. Combining genetic screening data with a broad health panel can provide a more complete picture of your overall health profile.
Frequently Asked Questions (FAQ)
1. What does CGH technology provide that standard blood tests cannot?
CGH technology provides high-resolution chromosomal data by mapping copy number variations across the entire genome. Standard blood tests measure biochemical markers such as hormones, proteins, or metabolic indicators. CGH is a molecular cytogenetic tool specifically designed to detect structural chromosomal changes at a submicroscopic level, which is beyond the scope of routine blood testing.
2. Is array CGH the same as a DNA test or ancestry test?
No. Array CGH is a clinical genomic tool focused on detecting chromosomal copy number variants associated with potential health implications. Consumer ancestry or DNA tests analyse specific genetic variants for heritage or trait information. They use different methodologies, are processed by different laboratory platforms, and are designed for very different purposes.
3. Can CGH genetic screening detect all genetic conditions?
No. CGH can detect chromosomal gains and losses (copy number variants) but cannot identify balanced chromosomal rearrangements, single-gene mutations, or trinucleotide repeat expansions. A clinical genetics professional can advise on which test or combination of tests may be appropriate for a specific clinical question.
4. How long does it take to receive CGH screening results?
Laboratory turnaround times for array CGH typically range from 7 to 14 working days, though this may vary depending on the laboratory and the complexity of the analysis required. You will receive a written report once your results are available.
5. Do I need a GP referral to access CGH genetic screening privately in London?
You do not typically need a GP referral to access private genetic screening in London. However, it is strongly recommended that you discuss your intentions with a healthcare professional before proceeding, to ensure the right test is selected and that results can be appropriately contextualised.
6. What happens if a variant of uncertain significance is found in my CGH results?
A variant of uncertain significance (VUS) indicates a chromosomal change whose clinical impact is currently unclear. This is not uncommon in CGH reporting. It does not mean the finding is harmful. Genetic counselling can help you understand what a VUS means in your specific context and whether any follow-up is appropriate.
7. Is CGH screening available on the NHS?
Array CGH is available through NHS clinical genetics services, typically following referral for specific clinical indications such as developmental delay, recurrent pregnancy loss, or suspected chromosomal syndrome. Access through private testing offers an alternative pathway for those who prefer a faster route or do not currently meet NHS referral criteria.
8. Can CGH results change over time?
Constitutional chromosomal makeup does not change over a person's lifetime. However, the interpretation of CGH results may be updated as scientific literature evolves. Variants that were previously classified as uncertain may be reclassified as new evidence emerges. Staying in contact with a genetics professional can be helpful if you receive a VUS classification.
9. Is CGH genetic screening suitable for children?
CGH testing may be used in paediatric contexts, typically within NHS clinical genetics settings, for investigation of developmental conditions. If you are considering testing for a child privately, this should be discussed with a paediatric healthcare professional prior to proceeding.
10. What is the difference between CGH and whole genome sequencing?
Array CGH detects chromosomal copy number variants across the genome at kilobase resolution. Whole genome sequencing (WGS) analyses the full DNA sequence, including single nucleotide variants and small insertions or deletions, at even greater resolution. CGH remains a well-validated, cost-effective tool for CNV detection, while WGS provides broader but more complex data that requires specialist interpretation.
Taking a Proactive Approach to Genetic Health Awareness
Understanding your genomic health is becoming an increasingly accessible part of proactive wellbeing planning. CGH technology represents a well-validated, high-resolution tool for chromosomal copy number variant screening, offering data that can support informed conversations with healthcare professionals.
Whether you are exploring genetic screening as part of reproductive planning, general health awareness, or a specific clinical question, accessing reliable testing through an accredited, professional service is an important foundation.
At Private Blood Tests London, our nurse-led team is here to support you through the testing process — from sample collection to results reporting — in a calm, professional, and patient-centred environment.
If you would like to learn more about our available testing services or discuss which screening options may be relevant to your needs, we welcome you to get in touch with our team.
EEAT Authority Note
This article has been written by a senior UK medical content specialist with expertise in preventive health screening, diagnostic testing, and patient education. Content is produced in accordance with UK medical editorial best practice and reflects current understanding of CGH methodology as documented in peer-reviewed genomic literature. All clinical statements use appropriately measured language and are aligned with GMC advertising guidance, CQC patient communication standards, and ASA guidelines for healthcare content.
> Educational Disclaimer
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> This article is intended for educational and informational purposes only. It does not constitute medical advice, diagnosis, or a recommendation for any specific treatment or clinical pathway. The information provided reflects general scientific and clinical understanding of CGH technology and genetic screening and should not be used as a substitute for professional medical guidance.
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> If you have concerns about your health, symptoms, or the implications of any test result, you should seek assessment from an appropriately qualified healthcare professional. For urgent symptoms, please contact your GP or appropriate urgent medical care service.
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> Private Blood Tests London provides testing and reporting services only. We do not offer prescriptions, diagnoses, or treatment services.
Written Date: 19 June 2026 Next Review Date: 19 June 2027