VendorInvestigate result on a Wuxi semaglutide lot lands 2.1 points below the supplier’s figure

Two laboratories analysing vials from the same semaglutide lot have returned figures 2.1 percentage points apart. VendorInvestigate reported 97.9%; PeptideMeter reported a lower number on a shallower gradient with a tighter integration threshold. Both results are defensible and the difference is entirely methodological, which is the point of publishing them together.

Reported figures across the set were: highest 97.9%, lowest 95.2%, median close to the midpoint of the two. Every report in the set stated a detection wavelength, and 15 of them stated an integration threshold. The Journal has asked the laboratory to publish thresholds on all reports as a matter of routine.

The Journal purchased 900 vials from the same lot and had 15 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.

Batch variance rather than vendor quality is the recurring finding of this programme. Across the 15 determinations the Journal has commissioned to date, within-vendor spread has been wider than between-vendor spread for two thirds of the companies tracked, which is an argument against rating any supplier on a single number.

"Content is the number that matters if you are doing arithmetic with a vial, and content is the number nobody sells," said Rowena Ashcombe, community pharmacist and diabetes educator. "Purity is what you can afford. Content is what you need."

QSC’s dossier has been updated with this determination and with the date of the request for comment. The dossier’s "what we could not verify" box records the questions still outstanding.