This is a ready-to-use worksheet for measuring the hold-up volume of a sterilizing filter and its downstream tubing, and stating its impact on batch yield, sized for low-volume, high-value programs where every milliliter of product matters. Replace every <<FILL: ...>> placeholder with your own specifics and route it through your normal document control, review, and approval. A worked filled sample row follows.
Document control header
| Field | Entry |
|---|---|
| Document title | Filter Hold-Up Volume and Yield Loss Characterization for <<FILL: product / process step>> |
| Document number | <<FILL: e.g. HUV-2026-01>> |
| Version | <<FILL>> |
| Effective date | <<FILL>> |
| Owner | <<FILL: e.g. Validation Lead / Process Development>> |
1. Instructions
Measure the fluid recovered from a validated blow-down, flush-through, or gravity-drain step performed after the batch itself has been collected, by weight or calibrated volume, for the filter and every length of downstream tubing between the filter and the fill point. Record the result as both an absolute volume and a percentage of total batch volume. State whether the recovered volume is charged against batch yield or recovered through a validated, qualified recovery step; a recovery step used to reclaim hold-up volume needs its own validation showing it does not compromise sterility or product quality.
2. Field table
| Field | Format | Required | Who records it | When |
|---|---|---|---|---|
| Batch ID | <<FILL>> | Yes | Manufacturing | At batch execution |
| Filter model / lot | <<FILL>> | Yes | Manufacturing | At batch execution |
| Downstream tubing length / bore | <<FILL>> | Yes | Manufacturing | At batch execution |
| Measurement method (weight / calibrated volume) | <<FILL>> | Yes | Manufacturing | At the blow-down/flush step |
| Measured hold-up volume | <<FILL>> | Yes | Manufacturing | At the blow-down/flush step |
| Total batch volume | <<FILL>> | Yes | Manufacturing | At batch execution |
| Hold-up as % of batch volume | Calculated | Yes | QC / Validation | Post-batch |
| Charged to yield, or recovered via validated recovery step? | <<FILL>> | Yes | Validation lead | Post-batch |
3. Acceptance / trending
| Criterion | Requirement |
|---|---|
| Measured hold-up volume within the range characterized during process development | Flag any result outside the characterized range for investigation |
| Recovery step, if used, independently validated | A recovery step is not assumed safe because it recovers value; it needs its own sterility and quality assessment |
| Trend across batches | Track hold-up volume batch to batch; a drifting value can indicate a tubing set, connector, or filter change that was not run through revalidation impact assessment |
4. Retention
Retain this record with the batch record per <<FILL: site retention policy>>, and reference it in the batch’s yield reconciliation.
Filled sample row
Extract for an example gene therapy fill step. Company, product, and numbers are illustrative.
| Batch ID | Filter model / lot | Tubing length / bore | Method | Measured hold-up | Total batch volume | % of batch | Disposition |
|---|---|---|---|---|---|---|---|
| ATX-520-B014 | <<FILL: model>> / Lot 22F | 0.8 m, 1/4 in bore | Weighed blow-down, calibrated scale | 35 mL | 2000 mL | 1.75% | Charged to yield; no recovery step used for this product given sterility risk of re-introducing recovered fluid |
Common inspection findings this worksheet prevents
- Hold-up volume never measured or characterized, discovered only as an unexplained yield shortfall.
- A recovery step used to reclaim hold-up volume with no validation of its own showing sterility and quality are preserved.
- No batch-to-batch trending, so a drifting hold-up volume from an undocumented tubing or connector change goes unnoticed.
How to adapt this worksheet
- Set your document number and product in the header.
- Define the measurement method once, by weight or calibrated volume, and use it consistently across batches so trending is meaningful.
- Decide up front whether hold-up volume is simply charged to yield or recovered through its own validated step; do not treat recovery as free.
- Trend the result across batches and route any drift into a revalidation impact assessment.