- [Resource Hub](/) - [Field Guide](/?resource-type=field-guide#library) - The 21 CFR Part 11 Cell-Counter Evaluation Checklist Field Guide · 6 min read · FDA / Regulatory # The 21 CFR Part 11 Cell-Counter Evaluation Checklist A practical scoring tool for evaluating any cell counter against the five requirements an audit-ready count has to meet for GMP cell-therapy release — before you buy. Key takeaways - Must-haves are pass or fail; differentiators break the tie. A counter that misses one must-have is not audit-ready for release, whatever else it does well — because you would close the gap yourself with middleware, a manual workaround, or a re-validation. - Five requirements gate an audit-ready count — data integrity native to the instrument, concordance with the method you already trust, precision on hard samples, viability and identity in one read, and a validation path with the uptime to keep it. - Volumetric counting holds count CV under 2 percent where image-based counters run 20 to 30 percent — the difference between a number you can defend and an argument with your auditor. - The Moxi GO II reference column is validated head to head in a peer-reviewed CAR-T manufacturing QC study (Pajarillo et al., Cytotherapy 2024): no significant difference on count and size versus a reference volumetric sizer, and r² of 0.97 (viability), 0.997 (CD4), and 0.90 (CAR19) versus a reference fluorescence analyzer. Every cell counter on the market will tell you it counts cells. Far fewer can prove the number to an auditor. This checklist scores any counter against the five things an audit-ready count has to do before it touches a GMP cell-therapy release workflow. If you run QC, Quality, MSAT, or IT for a cell-therapy program, the counter you choose is not just a number-generator — it is a record that has to stand up in review. The specifications that matter are not the ones on the front of the brochure. They are the ones an auditor asks about: who can change the data, how the change is recorded, whether the number agrees with the method you already trust, and whether you can validate the instrument into your workflow and keep it running through a campaign. Use the sheet below to score every counter on your shortlist against the same bar. The Moxi GO II column is filled in as a worked reference; the requirements are the point. ## How to use this checklist Score every counter you are evaluating on each line. A must-have (M) is pass or fail: a counter that misses one is not audit-ready for release, whatever else it does well, because you would have to close that gap yourself with middleware, a manual workaround, or a re-validation. A differentiator (D) breaks the tie between counters that clear every must-have. The Moxi GO II column is filled in as a reference; score your own candidates in the empty column and bring the completed sheet to a specialist. The two marks M — Must-have: pass or fail. Thirteen of them, total. Miss one and the counter is not release-ready as it stands. D — Differentiator: a tie-breaker among counters that already clear the must-haves. Seven of them, total. ## 1. Data integrity, native to the instrument The count supports a regulated release decision, so its record has to be provable without a middleware project. These are the controls 21 CFR Part 11 asks for around electronic records and electronic signatures. M / D Criterion Moxi GO II Your counter M An audit trail logs every data-modifying action. ✓ ☐ M An electronic signature is required on every change to the data. ✓ ☐ M Role-based access separates the person who runs the test, the person who reviews it, and the administrator. ✓ ☐ M Deletion is restricted to the administrator, and every deletion is logged. ✓ ☐ M Results export in a standard format (FCS 3.1 or equivalent) that both Quality and Manufacturing can open. ✓ ☐ D Part 11 controls run in the instrument’s own software — an activated Secure Mode compliance module — rather than a third-party middleware system you validate and maintain. ✓ ☐ ## 2. Concordance with the method you already trust A clean audit trail will not survive review if your reference method disagrees with the number. Before a counter earns a place in the workflow, it has to agree with the method your Quality team already accepts. M / D Criterion Moxi GO II Your counter M You can run it in parallel against your reference volumetric sizer on real product. ✓ ☐ M It shows no significant difference on concentration and size versus that reference method. ✓ ☐ M The concordance holds across the concentration range you actually run. ✓ ☐ ## 3. Precision you can defend on hard samples Cell-therapy material means small cells, debris, and low concentrations — the conditions where a wide coefficient of variation becomes an argument with your auditor rather than a footnote. M / D Criterion Moxi GO II Your counter M Count CV stays under 2 percent, against 20 to 30 percent for image-based counters. ✓ ☐ M Precision holds on small cells, debris, and low concentrations. ✓ ☐ D It measures by direct volume — tens of thousands of particles per test — rather than imaging a few hundred. ✓ ☐ ## 4. Viability and identity in the same read A release-grade count is rarely just a count. Splitting count, viability, and identity across three instruments slows turnaround and invites cross-instrument disagreement in exactly the record an auditor will read. M / D Criterion Moxi GO II Your counter M Viability (live or dead) reads in the same run as the count. ✓ ☐ D A CD4 or CAR identity marker reads in the same run as viability. ✓ ☐ D The consumable is a self-contained cassette with no reagent prep at the instrument. ✓ ☐ ## 5. A validation path and the uptime to keep it Native compliance only helps if you can validate the instrument into your workflow and keep it running through a campaign. This is where an evaluation that looked fine on paper either earns its place at-line or stalls. M / D Criterion Moxi GO II Your counter M An IQ/OQ validation package is available. ✓ ☐ M There is a documented bead-check or calibration cadence for a validated process. ✓ ☐ D A preventive-maintenance program is offered. ✓ ☐ D A zero-fluidics design means no sheath fluid, no daily cleaning, and no carryover between patient lots. ✓ ☐ D The footprint fits at-line, in or beside the biosafety cabinet. ✓ ☐ Reference tally The Moxi GO II column meets all 13 must-haves and all 7 differentiators . Score your own candidates the same way — count the must-haves met out of 13, then the differentiators out of 7 — and carry both totals into the read below. ## How to read your score If any must-have is unchecked The counter is not release-ready as it stands. You can still buy it, but budget for the middleware project, the manual workaround, or the re-validation that fills the gap — and add that to the real total cost of the instrument. If all must-haves are checked Compare the differentiators. The counter with more of them is the one your IT and Quality colleagues sign off on fastest, and the one that adapts as your panels evolve rather than locking you to a fixed channel. ## Where the Moxi GO II lands The Moxi GO II reference column is filled in for every must-have and differentiator above. Its counting concordance and its viability and phenotype readouts were validated head to head against the reference instruments a GMP lab already uses, in a peer-reviewed CAR-T manufacturing QC study from Penn Medicine (Pajarillo R, et al. Cytotherapy 2024;26(5):506–511; DOI 10.1016/j.jcyt.2024.01.007). Count and size showed no significant difference versus a reference volumetric sizer; viability, CD4, and CAR19 tracked a reference fluorescence analyzer. Measurement Moxi GO II result Compared against Count & size No significant difference a reference volumetric sizer Viability r² = 0.97 a reference fluorescence analyzer CD4 r² = 0.997 a reference fluorescence analyzer CAR19 r² = 0.90 a reference fluorescence analyzer What the reference column claims — and what it does not The Moxi GO II provides count, viability, and identity data; your validated method owns the release decision. The concordance above was established in one peer-reviewed CAR-T QC study; validate any counter against your own reference method and your own product before you rely on it for release. ### Score your shortlist against the same bar Bring your completed checklist to a Precision Cell Systems specialist. They can walk your Quality and IT colleagues through the Secure Mode audit-trail module, share the IQ/OQ validation package for your file, and help you plan an evaluation against the reference method you already run. [Talk to a Specialist](https://precisioncellsystems.com/request-a-quote/) For research use only. The instrument provides count, viability, and identity data; your validated method owns the release decision. On this page - [How to use it](#how-to-use) - [1 · Data integrity](#data-integrity) - [2 · Concordance](#concordance) - [3 · Precision](#precision) - [4 · Viability & identity](#viability-identity) - [5 · Validation & uptime](#validation-uptime) - [Reading your score](#reading-your-score) - [Where the Moxi GO II lands](#moxi-go-ii-reference) ### Evaluating counters for release? [Talk to a Specialist](https://precisioncellsystems.com/request-a-quote/) [Back to all resources](/#library) ## Similar resources [Field Guide](/resources/audit-ready-cell-counting-gmp-guide/) Moxi GO II 2026 ### Audit-Ready Cell Counting for GMP Cell-Therapy QC An educational field guide to the audit-ready framing and the five requirements of a count you can defend. [Read Field Guide](/resources/audit-ready-cell-counting-gmp-guide/) [Blog](/resources/gmp-cell-therapy-qc-counting-audit-ready/) Moxi GO II 2026 ### GMP Cell-Therapy QC Counting: What Makes a Count Audit-Ready The evergreen guide to what makes a GMP cell-therapy count audit-ready — the hub for the Part 11 and volumetric-vs-image explainers. [Read Blog](/resources/gmp-cell-therapy-qc-counting-audit-ready/) [App Note](https://precisioncellsystems.com/wp-content/uploads/2026/02/Moxi-Applications-Compendium.pdf) Moxi GO II Moxi V Moxi Z 2026 ### Applications Compendium Scientists are concerned with speed, accuracy, and convenience, and those running the lab and industries are concerned with the cost typically associated with high-performing instruments. Our proprietary Coulter Principle-based system delivers on all three accounts, and is therefore a perfect fit for any cell biology benchtop. [Download App Note](https://precisioncellsystems.com/wp-content/uploads/2026/02/Moxi-Applications-Compendium.pdf) [Blog](/resources/21-cfr-part-11-cell-counter-requirements/) Moxi GO II 2026 ### What 21 CFR Part 11 Requires of a Cell Counter The compliance explainer: what 21 CFR Part 11 actually demands of a cell counter — audit trail, e-signature, access control, and a Secure Mode. [Read Blog](/resources/21-cfr-part-11-cell-counter-requirements/) [Blog](/resources/cell-count-is-a-release-assay-cell-therapy/) Moxi GO II 2026 ### In Cell Therapy, Your Cell Count Can Serve as a Release Assay A demand-creation reframe: in GMP cell therapy, the cell count can function as a release assay — and what that shift means for how you count and prove it. [Read Blog](/resources/cell-count-is-a-release-assay-cell-therapy/) [Blog](/resources/volumetric-vs-image-based-cell-counting-cart-qc/) Moxi GO II 2026 ### Volumetric vs Image-Based Cell Counting for CAR-T QC The method explainer: volumetric vs image-based counting for CAR-T QC, and why the CV gap matters at lot release. [Read Blog](/resources/volumetric-vs-image-based-cell-counting-cart-qc/) [App Note](https://precisioncellsystems.com/wp-content/uploads/2026/02/Moxi-Applications-Note-Unlocking-the-Next-Stage-in-CAR-T-Cellular-Analysis.pdf) Moxi GO II 2026 ### Unlocking the Next Stage in CAR-T Cellular Analysis There are a variety of ways to monitor this process in cell culture, the two most prominent being cell counting via imaging-based and coulter-based cell counting methods and higher-level cellular analysis with fluorophore-tagged antibodies and fluorescent reporters via flow cytometry. While each instrument used to achieve these two things has its advantages and disadvantages, few and far between can do both at once. Out of all your options, no other instrument has the power to do both with the speed, precision, and ease that Precision Cell Systems' Moxi Go II can. In this document, we will take you through how you can unlock the next stage in your cellular analysis process for CAR-T with our instruments. [Download App Note](https://precisioncellsystems.com/wp-content/uploads/2026/02/Moxi-Applications-Note-Unlocking-the-Next-Stage-in-CAR-T-Cellular-Analysis.pdf) [Brochure](https://precisioncellsystems.com/wp-content/uploads/2025/12/Moxi_GO_II_Brochure.pdf) Moxi GO II 2025 ### Brochure - Moxi GO II [Download Brochure](https://precisioncellsystems.com/wp-content/uploads/2025/12/Moxi_GO_II_Brochure.pdf) [Publication](https://www.cell.com/iscience/fulltext/S2589-0042(25)01158-7) Moxi GO II 2025 ### Simulating CD8 T cell exhaustion: A comprehensive approach [View Publication](https://www.cell.com/iscience/fulltext/S2589-0042(25)01158-7) [Publication](https://pmc.ncbi.nlm.nih.gov/articles/PMC11259153/) Moxi GO II 2025 ### Streamlined measurement of chimeric antigen receptor T-cell concentration, size, viability and two-color phenotyping during manufacturing [View Publication](https://pmc.ncbi.nlm.nih.gov/articles/PMC11259153/) [Publication](https://pmc.ncbi.nlm.nih.gov/articles/PMC6167529/) Moxi GO II 2025 ### PET of adoptively transferred chimeric antigen receptor T cells with 89Zr-oxine [View Publication](https://pmc.ncbi.nlm.nih.gov/articles/PMC6167529/) [Field Guide](/resources/05-suboptimal-resolution/) Moxi GO II Moxi V Moxi Z 2026 ### The Suboptimal Resolution Problem: Why Your Cell Populations Look Merged Using an aperture much larger than necessary reduces sizing resolution by creating smaller signal differences between cell sizes. Cell populations that should be distinguishable appear merged when the aperture is too large for the cells being measured. Target 15-40% of aperture diameter for optimal resolution. If you're counting lymphocytes on M+ cassettes because it works, you're sacrificing the sizing resolution that S+ cassettes would provide. [Read Field Guide](/resources/05-suboptimal-resolution/)