Urine Culture vs. PCR vs. Metagenomics: What’s the difference between these UTI tests?

By Gabrielle Gleeson-Solomon, CEO of Tota
Scientific Review by Dr Nick Parkinson, PhD
What are the differences in UTI test types and which one should I choose?

If you've ever had a urine test or a vaginal swab, you might not have spent much time thinking about how the test actually works.

Most of us don't. We give our sample, wait for the results and hope they provide some answers as to what’s causing our symptoms. 

What many people don’t realise is that there isn’t just one type of lab test. Whether you're comparing a PCR vs culture UTI test or trying to understand how metagenomics fits in, the key thing to know is that different tests are designed to look for different things.

Some look for a handful of specific bacteria. Others search for some DNA of known microorganisms. And some, like Tota's metagenomic sequencing test, look at the entire DNA of the microorganisms in your urinary or vaginal microbiome. 

Understanding the difference can help explain why one test finds something while another doesn't. And why the right test depends on the question you're trying to answer. 

The quick comparison 

Let’s look at each in a little more detail. 

Urine culture: Best for straightforward UTIs

Urine cultures have been the standard laboratory test for suspected UTIs for decades. 

The process is simple. A sample of your urine gets spread onto a culture dish and left in a lab. If bacteria are present in high enough numbers and are able to grow under the laboratory conditions, they form visible colonies that the lab can identify.  

This approach works very well for many first-time, straightforward UTIs. E. coli causes 70 to 95% of uncomplicated infections, and a small group of other familiar bacteria account for most of the rest. Standard culture is designed to grow exactly these, which is why it finds them so reliably.

The challenge comes when the infection isn't caused by one of these common bacteria. Not all bacteria can grow under the standard laboratory conditions used for urine culture. Some grow slowly, some need different conditions, and some don't grow at all. If they don't grow during the test, they won't appear in the results.

For some people, that means their urine culture comes back as “negative” or “normal” despite them continuing to experience symptoms. The urine culture test hasn’t necessarily ruled out an infection, it may simply not have detected the bacteria that were present.

PCR: Great at finding specific infections 

Instead of trying to grow bacteria in the laboratory, PCR (Polymerase Chain Reaction) looks directly for the DNA of specific microorganisms in the sample. 

Think of it as searching for names on a guest list. If an organism is on the list, PCR is incredibly sensitive and can detect even tiny amounts of its DNA to report it as present. If it's not on the list, the test won't know it's there. 

This makes PCR an excellent choice when healthcare professionals already have a good idea of what they're looking for. For example, it's widely used to detect sexually transmitted infections because it can quickly and accurately identify specific organisms, such as chlamydia and gonorrhoeae.

The trade-off is that PCR can only detect the organisms it's been designed to look for. If the organism causing your symptoms isn't on that list, the test won't find it. Once again, you could be told your results are "normal", when in reality the test simply wasn't looking for the microorganism causing your symptoms. 

Metagenomics: often called a “sequencing test for UTIs”

You’ll sometimes see metagenomics described as a “DNA UTI test”. What it does is read the DNA of all the bacteria, fungi and other organisms in a sample, rather than looking for just one infection or a pre-selected list of organisms. 

This is the technology we use here at Tota for our urinary and vaginal microbiome tests. 

Rather than searching for a list of predetermined organisms like the PCR test, our third-generation metagenomic sequencing reads all the DNA in the sample and identifies what's there, along with how much of each microorganism is present.

By looking at everything that’s present, third generation metagenomics gives you a much broader picture of your urinary microbiome than a targeted test can. It doesn’t make assumptions about what it’s looking for. Instead, it shows you what’s actually there. Because it isn’t limited to a pre-selected list, it looks more broadly across what’s present in your sample. 

And if the results don’t identify any organisms that could reasonably be linked to your symptoms, that’s useful information too. It may suggest it’s time to explore other possible causes or explanations with your healthcare professional.

Which test is right for you? 

When comparing metagenomics vs urine culture, it's not about which test is "better". They simply answer different questions. A urine culture is designed to diagnose many straightforward UTIs, while metagenomics is designed to give you a much broader picture of your urinary microbiome.

If you've got a straightforward UTI, a urine culture is often the right place to start. If your healthcare professional is looking for a specific infection, PCR may be the best option.

But if you're trying to understand your urinary or vaginal microbiome, particularly after ongoing symptoms, recurring infections or repeated "normal" results, looking at the whole picture can provide information that more targeted tests simply aren't designed to capture.

Explore About Our Tests →

Sources

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5. UK Health Security Agency. Guidance for the detection of gonorrhoea in England, 2021. GOV.UK. GOV.UK PDF
6. Ferneyhough B, Roddis M, Millington S, Quirk J, Clements C, West S, Schilizzi R, Fischer MD, Parkinson NJ.. A highly accurate nanopore-based sequencing workflow for culture and PCR-free microbial metagenomic profiling of urogenital samples. BMC Urol. 2025. PubMed: 40022097

This article is for general information and does not replace medical advice. If you're experiencing new, severe, persistent or worsening symptoms, please speak to a GP or another qualified healthcare professional.