Lot traceability (revision 29)

Lot traceability is the property of a supply chain in which any given container can be linked back to the batch of material it was filled from, and forward from that batch to every container filled from it. It is what makes a certificate of analysis mean anything: a certificate describes a lot, and without traceability there is no established relationship between the lot it describes and the vial in hand.^[1]

The link is carried by the batch number and is only as strong as the weakest transfer in the chain. Every point at which material changes container, changes hands, or is combined with other material is a point at which the link can be preserved by record-keeping or lost by its absence.^[2]

Traceability is a documentary property, not an analytical one. No amount of testing on a vial establishes which lot it came from; that is established, or not, by records.

A lot, or batch, is a quantity of material produced in a single process run under conditions intended to be uniform throughout. Uniformity is the point: it is the assumption that licenses extending a determination made on a sample to the whole quantity.^[1]

The assumption is not automatic. A synthesis run purified in several chromatographic fractions may be homogenised into one lot or held as several; a lot filled over a long period may not be uniform in fill mass; and a "lot" assembled by combining material from separate runs is a lot by declaration rather than by production.

Because the definition is procedural rather than physical, the meaningful question about a lot number is what procedure assigned it. A number that identifies a synthesis campaign, a purification pool and a fill run supports a different inference from one assigned at the point of packing.^[3]

The last row is the most consequential. Repackaging into new containers with a newly assigned identifier and no back-reference severs the chain completely, and the resulting vial cannot be associated with any certificate however genuine that certificate is.^[2]

Consolidation is the second most consequential. Where a shipment draws several lots and the paperwork names one, every subsequent inference about the material is unsound, and this failure is invisible to the recipient.

A purchaser can observe only a few things, and none of them proves traceability — they are the observable consequences of it.

The lot identifier appears on the vial, on the certificate and on the shipping paperwork, and the three agree. The certificate is lot-specific rather than a product-level document reissued for every order. A request for a certificate covering a lot bought some time ago can be met from records rather than by reissuing a current document. Where a consignment contains more than one lot, the paperwork says so.^[4]

Conversely, a certificate carrying no lot identifier, or one whose identifier does not appear on the vial, describes an unidentified quantity of material. That is a documentary observation and not an allegation about the material itself: the material may be excellent, but the document does not attach to it.

Traceability also has a temporal dimension. Records have retention periods, and a supplier able to produce a certificate for a lot sold two years earlier is demonstrating a records system rather than a filing habit.^[1]

• Batch number
• Certificate of analysis
• Chain of custody
• Repackaging
• Good manufacturing practice
• Counterfeit peptide