Why a result on one vial says less than the trade needs it to
The condition on arrival is recorded by some services and not others, and it is one of the more informative lines in a report.
Testing Dispatch
Independent analysis puts a ERP exenatide lot at 95.8%, against 93.5% on the certificate
A reminder that a purity figure is the output of a method, and that methods differ.
A peptide content determination commissioned by the Journal on a 2 mg exenatide vial from ERP has returned 98% of the labelled mass, the balance being the counter-ion and residual water that every lyophilised salt carries. Chromatographic purity on the same vial was above 95.8%. The two numbers measure different things, and this is one of the few certificates in the trade to print both.
The Journal purchased 14 vials from the same lot at retail and had four of them analysed separately, in order to distinguish vial-to-vial variation from method variation. Vial-to-vial agreement was within 0.4 percentage points. Method-to-method disagreement was an order of magnitude larger.
Reported figures across the set were: highest 95.8%, lowest 93.5%, median close to the midpoint of the two. Every report in the set stated a detection wavelength, and 18 of them stated an integration threshold. The Journal has asked the laboratory to publish thresholds on all reports as a matter of routine.
Four independent services — Medutest, VendorInvestigate, and the two others operating in this market — carry the analytical burden for a trade that has no release-testing obligation of its own. Each is paid by whoever submits the sample, which is usually the vendor. The Journal’s position is that a submitter-pays model is workable but that its incentive structure has to be stated whenever a result is quoted as verification.
Lorcan Feeney, analytical services director at an independent laboratory, said the gap was predictable from the methods alone. "You can reconstruct almost the whole difference from the integration threshold. What you cannot reconstruct is why anyone thinks a number without a threshold is comparable to a number with one."
ERP’s dossier has been updated with this determination and with the company’s response to it. The dossier’s ordering box records the lead times, the minimum quantities and what a buyer should ask for at the point of order.
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