Sample Traceability: How One Lab Fixed Chain-of-Custody Gaps

Sample traceability and chain-of-custody management are the backbone of defensible lab results—and when they break down, the consequences show up fast during audits, client disputes, and OOS investigations. This post walks through exactly what went wrong at one mid-size contract lab, what they changed, and what that looked like in practice.

The Lab That Kept Failing the Same Audit Finding

Meridian BioAnalytics is a contract testing lab in the mid-Atlantic region serving pharmaceutical clients and nutraceutical manufacturers. They run roughly 1,200 samples per month across microbiology, chemistry, and stability testing.

For three consecutive ISO 17025 surveillance audits, Meridian received a nonconformity in the same area: incomplete chain-of-custody documentation. Specifically, auditors flagged that sample login records didn't consistently capture receipt condition, that sub-aliquot transfers between analysts had no timestamps, and that sample disposal records were stored separately from the original sample record—sometimes in a paper binder, sometimes in a shared drive folder with inconsistent naming.

None of these gaps caused a product recall or a client complaint. But they created a pattern that made auditors—and Meridian's own QA manager, Dana Reyes—uneasy. If something did go wrong, could the lab reconstruct exactly what happened to a sample from receipt to disposal? The honest answer was: not reliably.

What "Chain of Custody" Actually Requires in Practice

Chain of custody isn't just a phrase from crime dramas. In a QC lab context, it refers to the documented, unbroken record of who had a sample, when, under what conditions, and what they did with it. For ISO 17025 and GMP environments, that record needs to be:

• Continuous — no gaps between receipt, storage, testing, and disposal
• Tamper-evident — changes must be logged with a reason and the original entry preserved
• Linked — sub-samples, aliquots, and re-tests must trace back to the parent sample ID
• Retrievable — any authorized person should be able to pull the full history in minutes, not hours

Meridian's system failed on the third and fourth points. Their LIMS tracked the original sample through first-pass testing, but when a sample was split for a repeat test or sent to a second analyst for confirmation, that transfer wasn't captured in the system. It lived in an email thread or a handwritten note on the sample bag.

The Audit That Forced a Reckoning

The tipping point came during a client-led audit in Q2. A pharmaceutical manufacturer was qualifying Meridian as a testing partner for a stability program. Their auditor asked to see the complete chain of custody for three archived samples from a pilot batch tested eight months earlier.

Dana's team spent four hours pulling records from three different locations: the LIMS, a paper log at the sample receiving bench, and a spreadsheet one analyst had created to track re-test requests. Even then, there was a 90-minute window on one sample where the record showed it logged in at the receiving station but didn't show up in the analyst's queue until the next morning. No one could explain the gap with documentation.

The client auditor issued a formal observation. The pharmaceutical company put Meridian's qualification on hold pending corrective action.

How Meridian Rebuilt Their Traceability Workflow

Dana and her team did a process map of every point where a sample changed hands or state—from client drop-off to freezer storage to bench testing to archival to disposal. They identified nine handoff points. Only four were being captured consistently in any system.

Their corrective action focused on three structural changes:

1. Centralized Sample Login with Condition Capture

Every sample received now gets a timestamped login entry that includes receipt condition (intact, damaged, temperature excursion noted, etc.), the receiving analyst's name, and a photo attachment for anything flagged as non-conforming on arrival. This entry is the anchor point for the entire chain.

2. Aliquot and Transfer Logging at the Point of Action

When an analyst splits a sample or hands it to a colleague, they log the transfer in the LIMS before the sample leaves their hands. The sub-aliquot gets its own ID that links back to the parent. This sounds like extra work—and initially, some analysts pushed back. But Meridian made it faster by adding a quick-transfer screen to their LIMS workflow that pre-fills the parent sample data and only asks for the new custodian and purpose.

They piloted this on their chemistry bench in July. Within 60 days, 97% of intra-lab transfers were being captured in real time versus roughly 40% before.

3. Disposal Records Attached to the Sample Record

Sample disposal used to be a separate paper log. Now disposal is a terminal status in the LIMS, entered by the analyst who performs the disposal, with a timestamp and the applicable SOP referenced. The record lives with the sample—not in a binder across the room.

What the Before-and-After Looked Like at Meridian

Six months after rolling out the revised workflow, Meridian went through their next ISO 17025 surveillance audit. The chain-of-custody nonconformity did not recur.

More practically: when an OOS result came in on a pharmaceutical client's finished product sample in September, Dana's team was able to pull the complete sample history—receipt, storage temp log cross-reference, analyst assignments, aliquot splits, and instrument run sequence—in under 20 minutes. Previously, that kind of reconstruction had taken most of a day and still left gaps.

The pharmaceutical client that had put Meridian's qualification on hold completed their re-audit in October. Meridian was approved as a qualified testing partner.

Meridian used Aliquora as the LIMS platform for this rebuild, configuring the aliquot transfer and disposal workflows within their existing sample tracking module rather than building something custom.

Three Traceability Mistakes Labs Keep Making

Meridian's situation isn't unusual. The same pattern shows up repeatedly in labs that haven't formalized their chain-of-custody process:

Treating traceability as a logging task rather than a workflow. If traceability documentation happens after the fact—at end of shift, or when someone remembers—gaps are guaranteed. The record needs to be created at the moment of transfer or action.

Splitting the record across systems. Paper logs, spreadsheets, and LIMS data that don't talk to each other create the exact reconstruction problem Meridian faced. A single, linked record isn't just an auditor preference—it's what makes an OOS investigation actually workable.

No defined custodian at every stage. Chain of custody breaks when it's unclear who is responsible for a sample at a given moment. Every sample should have an assigned custodian in the system from login to disposal. If it's in a storage freezer with no active custodian, the storage location and access controls are the documented custody.

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Frequently Asked Questions

What is sample traceability in a QC lab?

Sample traceability is the ability to reconstruct the complete history of a sample—who collected or received it, how it was stored and handled, what tests were run on it, and how it was disposed of. Strong traceability means that record is complete, linked, and retrievable without manual reconstruction.

What is the difference between chain of custody and sample traceability?

They're closely related but not identical. Chain of custody specifically refers to the documented sequence of possession—who had the sample and when. Traceability is broader and includes test results, instrument data, environmental conditions, and disposal records. In practice, a complete chain-of-custody record is a core component of full sample traceability.

How do labs maintain chain of custody during internal transfers between analysts?

The most reliable method is to log the transfer in a LIMS at the moment it occurs, with the receiving analyst's name, timestamp, and purpose. Physical labels or barcodes that link to the digital record help ensure the sample in hand matches what's in the system. Avoid batch-logging transfers at end of shift—that's where gaps appear.

What do ISO 17025 auditors look for in sample chain-of-custody records?

Auditors typically want to see that records are continuous from receipt to disposal, that changes or discrepancies are documented with explanations, that sub-samples link back to parent samples, and that the records are retrievable in a reasonable timeframe. A paper log stored separately from the LIMS record is a common finding.

How long should labs retain sample chain-of-custody records?

Retention requirements vary by industry and client contract. Pharmaceutical labs working under GMP typically retain records for at least one year past the product's expiration date, or longer as specified by the client. ISO 17025 accreditation bodies generally require at minimum that records are retained for the duration defined in the lab's quality management system, often three to five years. Always check your specific regulatory and client requirements.