Lot CBR-THY-260403 measured less than 5 EU per vial against a threshold of 350. Other Crescent Bioresearch certificates from the same laboratory carry a threshold of 40. Each says PASS, and the word takes its meaning only from the threshold printed beside it.
ALBANY, N.Y., Oct. 22, 2026 — Crescent Bioresearch, a supplier of laboratory compounds, has published the Thymalin certificate of analysis for lot CBR-THY-260403. The endotoxin result is less than 5 EU per vial and the threshold is 350 EU per vial. Some of the company’s other certificates, issued by the same independent laboratory, carry a threshold of 40 EU per vial, and every one of them says PASS. A pass is read against the threshold printed beside it.
Thymalin, also known as Thymalinum and Timalin, a thymus peptide complex, CAS 63958-90-7, is supplied by Crescent Bioresearch as Thymalin 10 mg for laboratory research.
The Thymalin page
BTLabs, an independent laboratory in West Palm Beach, Florida, tested the lot on Sept. 24, 2026, by the Limulus amebocyte lysate (LAL) test under USP General Chapter 85, Bacterial Endotoxins Test, which measures lipopolysaccharide, the endotoxin shed by Gram-negative bacteria, in endotoxin units (EU). The 10 mg vial was dissolved in 2 mL. The laboratory found less than 5 EU per vial, a result it notes is below the limit of detection, and compared it with a threshold of 350 EU per vial using a lysate with a sensitivity of 0.05 EU/mL. The lot passed, and the result is less than 0.5 EU per milligram.
A threshold is chosen
The threshold is neither part of the test nor a property of the compound. It is chosen. On the Thymalin page, the laboratory states its threshold was established under USP Chapter 85 guidance. On the company’s 40 EU pages, the same laboratory states a different basis for its threshold. Both approaches are drawn from pharmaceutical practice, and neither was written for the work a research entity does with a laboratory compound. The research entity decides what limit its own work requires, and it can do that only when the result is printed beside the threshold.
Two passes, two standards
Set the Thymalin certificate next to one carrying a 40 EU threshold and read only the word PASS on each. The two look identical and they are not. One lot cleared 350. The other cleared 40, a standard almost nine times stricter. For the Thymalin lot the difference changes nothing, because a result below 5 clears both. For a lot measuring 120 EU per vial, it would decide everything: a pass against 350 and a fail against 40, on the same vial, from the same test.
A speeding ticket shows the same thing
A driver is pulled over and handed a speeding ticket. The ticket says the driver was speeding, but it does not show the speed recorded or the speed limit on that road. The driver cannot tell whether the car was going 26 in a 25 zone or 60 in a 25 zone, and cannot check whether the ticket is right. A proper ticket prints both numbers: the speed recorded and the limit.
An endotoxin certificate that says only “pass” has the same problem. It gives the verdict without the two numbers behind it. The Thymalin certificate prints both: a result of less than 5 EU per vial and a limit of 350 EU per vial. The limit matters because limits differ. Other Crescent Bioresearch certificates from the same laboratory use a limit of 40, and a lot measuring 120 EU per vial would pass against 350 and fail against 40.
Why both figures are needed
A pass is a comparison of a measured value against a threshold. Without the value, the reader does not know what was found. Without the threshold, the reader does not know what it was compared against. A certificate missing either one cannot be taken as true data, because no one else can repeat the comparison.
For this lot, a research entity can see that the pass was against 350 and that the result was below 5, and can apply its own limit. It can also judge whether endotoxin at that level could play any part in what it observes, apart from Thymalin itself. The Thymalin annotated endotoxin report marks the threshold line.
“Pass is a verdict, and a verdict depends on the standard it was reached against,” Crescent Bioresearch said. “On this certificate the standard is 350 and the result is under 5. On others the standard is 40. A pass whose standard cannot be seen cannot be judged.”
SOURCE DOCUMENTS
Bacterial Endotoxins Test report COA261647-006, issued by BTLabs, West Palm Beach, Florida, for Thymalin lot CBR-THY-260403, tested Sept. 24, 2026, by LAL; the company’s current endotoxin certificates from the same laboratory; USP General Chapter 85, Bacterial Endotoxins Test.
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