Independent analysis puts a QST dulaglutide lot at 95.4%, against 91.5% on the certificate

Two laboratories analysing vials from the same dulaglutide lot have returned figures 3.7 percentage points apart. PeptideMeter reported 95.4%; Janoshik 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.

The Journal purchased 9 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.

The Journal purchased 9 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.

Batch variance rather than vendor quality is the recurring finding of this programme. Across the 13 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.

Havel Novotný, independent laboratory quality manager, thought the split-sample design was the useful part. "A single result on a single vial is an anecdote with a decimal point. Pairs from one lot to two laboratories is the cheapest experiment that answers a real question."

QST’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.