It is not easy to put an exact number to the purity of the NHOst populations because the tests used are all functional assays: alkaline phosphatase production and bone mineralization, which unless you have synchronized cultures, not all the cells are doing the same thing at the same time.

Based on the cell morphology and other parameters, R&D would say the purity of the NHOst cultures is about 95%. Other cell types are large multinuclear cells (probably osteoclasts) which do not grow well and have no chance of overtaking the culture.