Medutest

Medutest is the fastest of the six laboratories and accepts the widest range of submissions, including several compound classes the others decline. Both properties make it a large and useful contributor to index breadth. The trade-off is mass resolution: Medutest's identity confirmation runs on a single-quadrupole instrument at unit resolution, which is adequate for confirming that a 4,113 Da species is present and inadequate for distinguishing species that differ by 1 or 2 Da.

The consequence is specific and the index enforces it. For the compound pairs where a small mass difference is the whole question — bremelanotide vs melanotan II (1 Da), hexarelin vs GHRP-6 (14 Da), reduced vs oxidised cyclic peptides (2 Da), deamidated vs parent (1 Da) — a Medutest identity confirmation is recorded as "consistent with" rather than "confirmed", and the record page states which alternative species were not excluded. This is not a criticism of the laboratory; it is a description of what a unit-resolution instrument can and cannot do.

Measured bias is +0.08 pp on 166 paired comparisons, with the widest limits of agreement of the three high-volume labs at ±0.52 pp. The 25-minute gradient is at the index's minimum acceptable length for the acylated incretins.