A breeder's guide to dog DNA test accuracy and quality

A DNA health certificate is only as reliable as the laboratory process behind it. Two certificates can show the same word, "Clear", but how much confidence that word deserves depends on how the sample was handled, which controls were run, and who checked the result.

If you're planning litters for spring 2027, now is the time to test. Results back before your bitches come into season give you time to choose a stud with confidence. And with puppy buyers increasingly asking to see and verify test certificates, you need results you can stand behind.

This guide explains what happens to your swab once it reaches our lab, the difference between quality control and quality assurance, and where errors really come from.

What happens to your sample, step by step

1. Collection. You swab the dog's cheek and fill in the sample form. This is the only step the lab can't see, and as we'll explain below, it's where most problems start.
2. Receipt and registration. When you order we assign a swab for each line item on your order and give it a unique identifier (a barcode). When your swab arrives back with us we scan the barcode, and our lab system automatically tells you that we've received your swab. At this point, it's worth checking whether the information you gave us about the animal the swab was used on is correct. You can only make amendments to things like name, registrations or dates of birth before we report out the results.
3. DNA extraction. DNA is released from the cheek cells and purified. We have an automated robotic process for this step, which means that many samples can be processed at the same time without contamination risk.
4. Genotyping. The DNA is tested with an assay designed to detect one specific variant. Each run includes control samples of known genotype (clear, carrier and affected) and a blank with no DNA at all. If the controls don't give the expected results, the whole run is rejected.
5. Result calling and review. The raw data is interpreted to call each dog clear, carrier or affected. Calls that fall outside defined thresholds are repeated rather than forced. 
6. Reporting. The certificate is issued against the dog's microchip number and sample ID, naming the exact test and variant. Every step is traceable, so the lab can show how any certificate was produced.

Quality control vs quality assurance

The two terms are often used interchangeably, but they mean different things, and a reliable lab needs both.

QC catches a problem on the day. QA is what stops the same problem happening again, and what lets the lab show its working when a result is questioned.

Where DNA test errors actually come from

When a result turns out to be wrong, the cause is far more often outside the instrument than inside it.

Sample identity. The wrong dog swabbed, swabs swapped between littermates, or a form filled in for one dog and attached to another. No laboratory control can detect that a correctly processed sample came from a different dog. That's why identity at collection matters so much, and why some breeders choose vet-witnessed sampling with microchip scanning.

Contamination. A puppy that has just suckled, dogs sharing a food bowl, or a swab that touched another dog can produce a mixed DNA profile. Mixed samples can make a clear dog look like a carrier, or mask a result altogether. A good lab flags them for resampling.

Too little DNA. Swabs taken lightly, or left damp in a sealed packet, can yield too little usable DNA. In this case we report your results as "insufficient sample" and send you a new swab.

The wrong variant is ordered by the customer. Some conditions have several genetic forms. PRA is the best-known example: PRA-prcd and PRA-cord1 are caused by different variants in different genes, so a clear result for one says nothing about the other. It's always worth checking with our customer services team before you order to ensure that you're ordering the right test for your breed.

Unexpected variation at the test site. DNA assays detect a target sequence. Rarely, a second, unrelated variant close to that site can stop the assay binding to one copy of the gene, so a carrier reads as clear or affected. Well-designed assays are checked against this, and labs that see an unusual pattern repeat or retest by a second method.

Hereditary clear status carried too far. A dog recorded as clear by parentage is only as reliable as its pedigree. Recording errors or an unrecorded sire break the chain. If in doubt, test.

Taking a good swab

Since sample collection is where most errors occur, a few habits make a real difference:

• One dog at a time. Swab, label and seal each sample before you pick up the next dog.
• Keep dogs apart beforehand. Follow the no-food, no-drink and separation timings in your kit instructions. Don't swab puppies straight after they've suckled or played together.
• Scan the microchip as you swab. Write the number on the form there and then, rather than copying it from paperwork later.
• Swab firmly. Rub the inside of the cheek for the full time stated, so the swab picks up cells, not just saliva.
• Let it air-dry. A damp swab sealed in a packet can degrade before it reaches the lab.
• Consider a vet-witnessed sample for stud dogs, or any dog whose results buyers will rely on. It adds independent confirmation of identity that no lab can provide on its own.

Testing for spring litters

Our breed health panels cover the DNA tests relevant to each breed in one order, from a single cheek swab per dog.

• Testing several dogs? Our multi-dog discount is applied automatically at checkout: 10% off two dogs, 20% off three or more.
• First order with us? Use code NEWCUSTOMER for 10% off.

The two offers can't be combined. If you're testing three or more dogs, the multi-dog discount is the better deal, so you don't need the code.

Frequently asked questions

How accurate are dog DNA tests? A well-validated assay run with proper controls is highly reliable. Most wrong results come from sample mix-ups or contamination when you collect the sample, not from the test itself.

Can a DNA test give a false clear result? Yes, though it's uncommon. Causes include a sample from the wrong dog, testing for the wrong variant of a disease, or an unrelated variant interfering with the assay. 

What is the difference between quality control and quality assurance? Quality control is the set of checks within each test run. Quality assurance is the wider system of validated methods, procedures, training, tracking and audits that makes every run reliable.

Why did my dog's sample fail? Usually because the swab collected too little DNA, or the sample was contaminated during collection or degraded during transit. A resample nearly always fixes it.

Should I use vet-witnessed sampling? It's worth considering for stud dogs and breeding stock whose results buyers will rely on. It provides independent confirmation of the dog's identity at the point of collection.