"That's short for Variable numbers of tandem repeats.'

So far, 12 genotypes, spread over the world, have been discriminated, based on a variable number of tandem repeats and mycobacterial interspersed repetitive units.

This has now been superseded by variable numbers of tandem repeats (VNTR), which is technically easier to perform and allows better discrimination between strains.

One GPIbα polymorphism is referred to as "VNTR" because it consists of a variable number of tandem repeats of 39 base pairs, each repeat leading to a 13-amino acid addition that pushes a vWF-binding domain further away from the platelet membrane surface.