titre

noun

ti·​tre

chiefly British spelling of titer

1

: the strength of a solution or the concentration of a substance in solution as determined by titration

… if the analyst is using an oxalic acid solution to titrate a solution of calcium oxide, the titer of the oxalic acid solution would be expressed as its CaO titer, or the weight of CaO that is consumed by 1mL of the oxalic acid solution.

—John Kenkel

2

: a measure of the concentration of a substance (such as an antibody) in a blood sample that is obtained by subjecting the sample to serial dilutions (as with saline) to determine the maximum dilution at which the sample retains a specific activity (such as neutralizing an antigen) and that is often expressed as a ratio (such as 1:200)

I have examples of people who clearly were infected who are antibody negative. They probably have such a low titer of antibody that it's below the level of the cutoff.

—Anthony Fauci

The Blood Center will also ensure that the plasma has high titers of antibodies against the coronavirus.

—John Timmer

also : a test for obtaining a blood titer

—often used before another noun

an antibody titer test

Medical Definition

titre

chiefly British variant of titer