Testing for >1000 conditions using your DNA

Understanding Stats in Genetics

Genetic testing can reveal powerful insights about your health. But behind every result is a foundation of statistics that helps us interpret your DNA accurately.

Book now

Book Now

Speak to a Genetic Counsellor Today

How it works

Chat with our Genetic Counsellor, receive your at-home DNA kit with a quick cheek swab, send it back, and get your results in under 4 weeks.

Why Statistics Matter?

Genetic testing doesn’t just say “yes” or “no” – it estimates probabilities. We look at patterns in your DNA and compare them to scientific data from thousands of people to understand what’s typical, what’s rare, and what might affect your health. Below is a simple guide to help you understand what these numbers really mean.

Key terms.

Genetic test results can seem complex, these six key terms help explain how reliable the results are.

Prevelance

Condition Rate In The Population

Prevalence refers to how many people in a given population carry the gene variant or have the condition. The more common it is, the more it affects the PPV and NPV of the test. In short, prevalence helps shape how useful a test result will be in the real world.

Sensitivity

The True Positive Rate

A test with high sensitivity correctly identifies most people who actually carry the gene variant. In other words, the higher the sensitivity, the more likely it is that if you do have the variant, the test will detect it.

Specificity

The True Negative Rate

A test with high specificity correctly identifies most people who do not carry the gene variant. In other words, the higher the specificity, the more likely it is that if you don’t have the variant, the test will report a negative result – and avoid a false alarm.

Positive Predictive Value

The Chance a Positive Result Is True

Positive Predictive Value (PPV) tells you how likely it is that you actually have the condition or variant if your test result comes back positive. A high PPV means that most people who test positive truly carry the variant. This value depends not just on the test's accuracy, but also how common the condition is in the population being tested.

Negative Predictive Value

The Chance a Negative Result Is True

Negative Predictive Value (NPV) tells you how likely it is that you don’t have the condition or variant if your test result is negative. A high NPV means that most people who test negative truly don’t carry the variant. Just like PPV, this depends on the test’s accuracy and how rare or common the condition is.

Test Accuracy

How Often The Test Gets It Right

Test accuracy shows the overall chance that the test result — positive or negative — is correct. It combines both sensitivity and specificity to give you a big-picture view of how reliable the test is.

Type of Cancers

We offer expert advice and testing for a range of genes that may increase your risk of developing certain types of cancer.

View Full Gene List

Interactive explainer

Learn about how genetic test accuracy varies based on Sensitivity, Specificity, PPV, NPV and Prevelance.

Genetic Testing Performance Metrics - NIPT, Cancer & Carrier Screening

Without Condition

With Condition

Test Threshold

Sensitivity

99.0%

TP / (TP + FN)

Specificity

99.5%

TN / (TN + FP)

PPV

95.2%

TP / (TP + FP)

NPV

99.9%

TN / (TN + FN)

Condition Prevalence:

1:10,000

1:100 1:1K 1:10K 1:100K 1:1M 1:10M

Test Sensitivity:

99%

Test Specificity:

99.5%

Understanding Genetic Testing Metrics

Sensitivity: How well the test detects people who actually have the genetic condition.

Specificity: How well the test correctly identifies people without the condition.

PPV: If your test is positive, what's the chance you actually have the condition?

NPV: If your test is negative, what's the chance you don't have the condition?

Key Insight: PPV varies dramatically with condition prevalence, even with excellent test performance.

Genetic Testing Performance Metrics - NIPT, Cancer & Carrier Screening

Without Condition

With Condition

Test Threshold

Sensitivity

99.0%

TP / (TP + FN)

Specificity

99.5%

TN / (TN + FP)

PPV

95.2%

TP / (TP + FP)

NPV

99.9%

TN / (TN + FN)

Condition Prevalence:

1:10,000

1:100 1:1K 1:10K 1:100K 1:1M 1:10M

Test Sensitivity:

99%

Test Specificity:

99.5%

Understanding Genetic Testing Metrics

Sensitivity: How well the test detects people who actually have the genetic condition.

Specificity: How well the test correctly identifies people without the condition.

PPV: If your test is positive, what's the chance you actually have the condition?

NPV: If your test is negative, what's the chance you don't have the condition?

Key Insight: PPV varies dramatically with condition prevalence, even with excellent test performance.

Another 23 & Me?

At Jeen, we focus on health, not hair colour. Our genetic testing uses 50x sequencing depth for greater accuracy and confidence in detecting inherited conditions.

How DNA Sequencing Works

DNA is broken into small fragments, sequenced, and computationally assemble into the full genome.

What is Sequencing Depth?

Sequencing depth is how many times your DNA is read. Higher depth = more accurate results, lower depth = risk of missed mutations.

Genome Size Matters!

Larger genomes (like humans) need more sequencing reads. That’s why high-depth testing matters—it ensures nothing is missed.

Why Jeen?

Not all genetic tests are created equal. At Jeen, we use 50x sequencing coverage, which means each section of your DNA is read around 50 times. Here’s why it makes a difference:

Bigger genome → more data needed

Higher depth → better accuracy

Balance cost vs. detail!

What Now?

Have questions? We’re here to help. Genetic testing can feel overwhelming—but it doesn’t have to be. Our NHS-trained genetic counsellors are here to walk you through your options, explain the science in plain English, and help you decide if testing is right for you.

Genetic
Counselling

Get started

Frequently
Asked Questions

Why do sensitivity and specificity matter when choosing a genetic test?

Sensitivity and specificity help you understand how reliable a test is. A test with high sensitivity catches more true positives, and one with high specificity avoids false alarms. Together, they help ensure your results are trustworthy.

If a test is highly accurate, can I skip seeing a genetic counsellor?

Not quite. Even highly accurate tests need interpretation. A genetic counsellor helps explain what your result means for you and your family — and whether you need any follow-up or additional screening.

Why are sensitivity and specificity important in genetic testing?

These metrics help determine a test's accuracy. High sensitivity ensures most carriers are identified, while high specificity ensures non-carriers aren't misdiagnosed. Together, they provide a comprehensive view of a test's reliability.

What is the difference between test sensitivity and PPV?

Sensitivity measures how well a test identifies true positives among all who have the condition, while PPV assesses the likelihood that a positive test result is a true positive. Sensitivity is intrinsic to the test, whereas PPV is influenced by the condition's prevalence in the population.

What can affect how accurate my genetic test result is?

Several things can influence test accuracy — including how common the gene variant is in the population (prevalence), the quality of the lab, and even how the sample was collected. That’s why expert-designed tests and genetic counselling matter.

Why do different sources give different numbers for test accuracy?

Test stats like sensitivity or PPV can change based on the population being tested, the condition being looked for, and how the test is used. That’s why context matters — Jeen’s team explains your results in a way that fits your unique case.

Can a test have high sensitivity but low specificity?

Yes. A test designed to catch all potential cases (high sensitivity) might also capture individuals without the condition, leading to false positives and thus lower specificity. Balancing both metrics is crucial for accurate testing.

Should I consult a genetic counsellor before and after testing?

Yes – and it’s a key part of your journey with Jeen. Our genetic counsellors are here to help you understand what your results mean and guide you through everything, including terms like sensitivity and specificity. You’ll have a counselling session before your test to explain what we’re looking for and what the results could mean. If your result shows something unusual, we’ll contact you and arrange a follow-up session. Even if your results are normal, you're always welcome to book another session if you'd like to talk them through with our team.

Get in touch

Our team of expert Genetic Counsellors is here to help. Whether you're curious about testing, your results, or what’s right for you — we're just a message away.

my@jeen.health

WhatsApp Us

Thank you

Thanks for reaching out. We will get back to you soon.

Oops! Something went wrong while submitting the form.

Understanding Stats in Genetics

How it works

1

2

3

Why Statistics Matter?

Key terms.

Genetic test results can seem complex, these six key terms help explain how reliable the results are.

Prevelance

Prevalence refers to how many people in a given population carry the gene variant or have the condition. The more common it is, the more it affects the PPV and NPV of the test. In short, prevalence helps shape how useful a test result will be in the real world.

Sensitivity

A test with high sensitivity correctly identifies most people who actually carry the gene variant. In other words, the higher the sensitivity, the more likely it is that if you do have the variant, the test will detect it.

Specificity

A test with high specificity correctly identifies most people who do not carry the gene variant. In other words, the higher the specificity, the more likely it is that if you don’t have the variant, the test will report a negative result – and avoid a false alarm.

Positive Predictive Value

Negative Predictive Value

Test Accuracy

Test accuracy shows the overall chance that the test result — positive or negative — is correct. It combines both sensitivity and specificity to give you a big-picture view of how reliable the test is.

Type of Cancers

Type of Cancers

Breast Cancer

Ovarian Cancer

Prostate Cancer

Pancreatic Cancer

Colorectal Cancer

Nervous System Tumors

Stomach Cancer

Endometrial Cancer

Retinoblastoma

Lobular Breast Cancer

Brain Cancer

Leukemia

Thyroid cancer

Melanoma

Lymphoma

Adrenal Gland Tumors

Kidney cancer

Cervical Cancer

Sarcomas

Lung Cancer

Interactive explainer

Genetic Testing Performance Metrics

Understanding Genetic Testing Metrics

Genetic Testing Performance Metrics

Understanding Genetic Testing Metrics

Another 23 & Me?

How DNA Sequencing Works

What is Sequencing Depth?

Genome Size Matters!

Why Jeen?

What Now?

GeneticCounselling

FrequentlyAsked Questions

Why do sensitivity and specificity matter when choosing a genetic test?

If a test is highly accurate, can I skip seeing a genetic counsellor?

Why are sensitivity and specificity important in genetic testing?

What is the difference between test sensitivity and PPV?

What can affect how accurate my genetic test result is?

Why do different sources give different numbers for test accuracy?

Can a test have high sensitivity but low specificity?

Should I consult a genetic counsellor before and after testing?

Get in touch

Thank you

Genetic
Counselling

Frequently
Asked Questions