How Countable PCR outperforms digital PCR for rare event detection – broader dynamic range is just the beginning

Comparing rare events to benchmarks shouldn’t be apples-to-oranges. Yet that’s exactly the position digital PCR (dPCR) puts you in — forcing side-by-side comparisons from separate runs, with diluted samples and variable input.

dPCR blocks you because of its partition processing limits and narrow dynamic range.

Countable PCR has 6-log dynamic range, which means rare and common targets coexist in one reaction — measured directly, without dilutions or multiple runs. That’s how you detect rare events with statistical confidence and biological accuracy. Now, you have the flexibility to design better experiments for rare event detection.

Run pre-amplification protocols without wrecking your comparison

Cell-free DNA from liquid biopsies doesn’t offer a lot of target to work with. To detect variants with any statistical confidence, you need to pre-amplify the sample. 

But, when you amplify the common events alongside the ultra-rare ones, the number of targets gets too high to run in dPCR. You have to dilute again and run a separate reaction.

That breaks the one thing you need most: a direct comparison of variant to wild-type (WT).

With Countable PCR, pre-amplify your entire sample, then measure both the variant and the WT in the same reaction. No dilutions, and no additional runs. The 6-log range lets you measure it all together — even when common targets are orders of magnitude higher than rare ones.

The result is a direct VAF% calculation from a single prep, giving clearer insight and tighter confidence intervals (Figure 1).

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                                         Figure 1

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Load more DNA. Find more rare events

Sometimes your rare target is just that rare — you need to scan more material to find it. Traditional dPCR systems cap out around 100,000 targets. Worse, dPCR loses a lot of your volume to microfluidics or sample handling.

To compensate, you're left hyperwelling — splitting samples into multiple reactions and stitching results together. That introduces pipetting errors and still doesn’t give you direct comparison of rare and common events.

Countable PCR skips the drama. Load up to 35 µL or 1 µg of DNA in a single tube. With that 6-log dynamic range, you’re still able to measure common events while spotting the rare ones (Figure 2).

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                                                  Figure 2

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With high input volume and broad dynamic range rare events finally get spotted

With dPCR, rare event detection leads to hacking together different experiments just to get usable data. You run multiple reactions while crossing your fingers that your dilutions are accurate. And still end up reporting VAF%s that are indirect comparisons of rare and common events.

Countable PCR handles a lot of sample, and it counts everything. You’ll get clean, actionable VAFs where rare and common are counted together — giving you a much truer reflection of biology.

Ready to leave hours of extra experiments behind?

Countable PCR gives you sensitivity that scales — and comparisons that actually compare.