This is a ready-to-use log for trending the system-suitability parameters of a relative-potency bioassay or ELISA over time. Trending catches slow drift, an aging cell line, a shifted reagent lot, a creeping EC50, months before it fails a batch. This is continued method verification, the assay equivalent of continued process verification. Replace every <<FILL: ...>> placeholder and maintain it continuously. A filled specimen follows. This is general guidance to adapt and verify, not legal or regulatory advice.
Header
| Field | Entry |
|---|---|
| Assay / product | <<FILL>> |
| Method reference | <<FILL: validated method ID>> |
| Reportable value format | <<FILL: e.g. geometric mean of 3 assays>> |
| Trending owner | <<FILL: role>> |
| Review cadence | <<FILL: e.g. monthly + at each reference/reagent lot change>> |
Field definitions
| Field | Format | Required | Who | When |
|---|---|---|---|---|
| Run ID | Text/ID | Yes | Analyst | Each run |
| Date | Date | Yes | Analyst | Each run |
| Analyst | Initials | Yes | Analyst | Each run |
| Cell passage number (cell-based) | Integer | Yes (cell-based) | Analyst | Each run |
| Reference standard lot | Lot ID | Yes | Analyst | Each run |
| Critical reagent lots (conjugate, coating, etc.) | Lot IDs | Yes | Analyst | Each run |
| Reference EC50 | Value + units | Yes | System | Each run |
| Signal window (D minus A) | Value | Yes | System | Each run |
| Control-well CV | % | Yes | System | Each run |
| Parallelism (reference-vs-reference) | Pass/Fail | Yes | System | Each run |
| Edge/positional control result | Value | Yes | System | Each run |
| Run disposition | Valid / Invalid | Yes | Reviewer | Each run |
| Comment (lot change, trend note, investigation) | Text | If applicable | Reviewer | As needed |
Trend limits and alerts
Define the control expectations so a trend is actionable, not just recorded.
| Parameter | Expected / alert |
|---|---|
| Reference EC50 | <<FILL: mean +/- limit; alert on drift or run outside window>> |
| Signal window (D minus A) | <<FILL: minimum; alert on downward trend>> |
| Control-well CV | <<FILL: maximum; alert on rising trend>> |
| Parallelism pass rate | <<FILL: expected pass rate; alert on rising non-parallel rate>> |
Actions on an alert: <<FILL: e.g. investigate cell line age or reagent lot; assess need for a new working cell bank or reagent bridge; notify QC management>>. A reference or critical-reagent lot change is always annotated on the trend so a step-change can be attributed rather than chased.
Acceptance criteria for the trending program
- Every run’s suitability parameters are captured, including invalid runs.
- Reference and critical-reagent lot changes are annotated on the trend.
- Trend limits are defined and reviewed on the stated cadence.
- An adverse trend triggers a documented action before a batch fails.
References
USP <1032>-<1034> (bioassay design, validation, analysis). ICH Q2(R2) and Q14 (analytical lifecycle and continued verification). ICH Q6B (specifications) for the potency requirement the assay supports.
Describe these compendial chapters in your own words; do not paste their text. Confirm the current version before use.
Filled specimen
The following shows several rows for an example reporter-gene assay, illustrating a reagent-lot step-change caught by trending. Illustrative only.
| Run ID | Date | Passage | Ref lot | Conjugate lot | Ref EC50 (ng/mL) | Signal window (RLU) | Control CV | Parallelism | Disposition | Comment |
|---|---|---|---|---|---|---|---|---|---|---|
| RGA-2605-009 | 12 May 2026 | 14 | REF-07 | CONJ-21 | 4.05 | 46,900 | 6.4% | Pass | Valid | - |
| RGA-2605-018 | 22 May 2026 | 18 | REF-07 | CONJ-21 | 4.18 | 45,200 | 7.1% | Pass | Valid | - |
| RGA-2606-005 | 04 Jun 2026 | 21 | REF-07 | CONJ-22 | 4.72 | 41,800 | 9.8% | Pass | Valid | New conjugate lot CONJ-22 in use |
| RGA-2606-014 | 14 Jun 2026 | 23 | REF-07 | CONJ-22 | 4.88 | 40,100 | 10.6% | Pass | Valid | EC50 drift + CV rise continues on CONJ-22 |
Interpretation: reference EC50 stepped up from ~4.1 to ~4.7-4.9 ng/mL and control CV rose from ~6% to ~10% exactly when conjugate lot CONJ-22 came into use. Runs still passed suitability, but the trend flagged a reagent-lot effect before any run failed. The documented action was to formally bridge CONJ-22 against CONJ-21, tighten the reference EC50 alert, and assess whether CONJ-22 should be quarantined. Without the trend annotation on the lot change, this would have looked like an unexplained method drift and cost weeks to diagnose.
Common inspection findings this log prevents
- No trending of system suitability, so slow drift is invisible until a batch fails.
- A reference or reagent lot change with no bridging and no trend annotation, producing an unexplained step in the potency trend.
- Invalid runs excluded from the trend, hiding a rising failure rate.
- Trend data recorded but with no defined limits or actions, so nobody acts on a clear drift.
How to adapt this log
- Set the trend limits and alert rules from your method’s own development and validation data.
- Add assay-specific columns (for ELISA: coating lot, minimum required dilution controls; for cell-based: plating density, confluence).
- Wire the log to your validated data system so values are captured, not transcribed.
- Tie an alert to your reference-standard and critical-reagent bridging procedure.
- Confirm the current version of each compendial chapter before use.