> For the complete documentation index, see [llms.txt](https://help.sbtinstruments.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://help.sbtinstruments.com/advanced/measurements-explained/limits-of-detection.md). # Limit of detection BactoBox® counts individual particles. If there are too *few* particles, the concentration estimate is too uncertain. If there are too *many* particles, we can't tell them apart. Therefore, we have limit of detection (LoD). BactoBox® outputs concentrations in these ranges: * 30 000–5 000 000 **cells/mL** (3·10⁴ to 5·106 cells/mL) * 30 000–5 000 000 **total/mL** (3·10⁴ to 5·106 total/mL) {% hint style="success" %} ## Target 0.5–4 million cells/mL for fast results The more things to count, the faster we are certain about the concentration. Give BactoBox® something to work with and it triggers the *Fast results* feature :fast\_forward:. Make a dilution series and [**measure the most diluted sample first**](/advanced/advanced-sample-preparation/hit-the-right-concentration/dilute-1-100.md#measure-the-most-diluted-sample-first). Aim for 0.5–4 million cells/mL. {% endhint %} The figure below shows how the LoD influences the BactoBox® output. The figure uses *total/mL* as an example but the very same thing is true for *cells/mL*. Limit of detection (LoD) and how they influence the BactoBox® output. {% hint style="info" %} ## Don't know the concentration of your sample? Make a dilution series and [**measure the most diluted sample first**](/advanced/advanced-sample-preparation/hit-the-right-concentration/dilute-1-100.md#measure-the-most-diluted-sample-first). This avoids clogging your BactoBox® setup. It also avoids carry-over from your previous sample vial. Once you are above the lower limit of detection (30 000 cells/mL), target 0.5–4 million cells/mL. {% endhint %} ## Above the upper limit Cross the upper limit and BactoBox® can no longer tell the particles apart, so it stops with an error instead of a result. A concentration above 5 000 000 particles/ml also risks clogging the flow cell.
BactoBox® error screen: Error 3000, too many particles (above 5 000 000 particles/ml). Discard sample, clean device and use a higher dilution.

Above the upper limit, BactoBox® shows Error 3000 instead of a result.

Discard the sample, clean the device, and measure again at a higher dilution. ## Single cell at a time The following figure shows how both too *few* and too *many* cells cause trouble.
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