A very recent deve­lo­p­ment is the abili­ty to deter­mi­ne the HLA cha­rac­te­ristics of a poten­ti­al stem cell donor wit­hout having to take a blood sam­ple. This can now be done by using a cot­ton stick to swab the mucous mem­bra­ne of the mouth. Befo­re any stem cells are dona­ted, howe­ver, a blood sam­ple will still be requi­red from the poten­ti­al donor for later tests.