What is phenotyping of blood during transfusion process?
In response to the above q. many have commented that the process is only limited to Middle Eastern countries....I think the term 'only' will be better substituted by 'mainly', the reason to which , is explained later ....

Now, the main clarification lies in the fact that, 


  ....there are more than 600 known antigens besides A and B that
  characterize the proteins found on a person's red cells. A combination
  of some of these less familiar but commonly occurring antigens are
  absent from the blood of an extremely small percentage of the
  population. There are also a few antigens that almost all people have
  on their red cells but that some lack. - One In A Million
  American Rare Donor Program


Now patients receiving a 1st time transfusion normally do not show any reactions or cross-matching problems with these blood subgroups but during repeated transfusion process like in case of thallaesemia , the receiver's blood gets sensitized against the donor's blood &amp; the problems ensues...


  Dr Therese Callaghan said, “All other antibodies are unexpected and
  are of two distinct types, alloantibodies (which target an antigen
  that is not present on your own red blood cells) and autoantibodies
  (which target an antigen that is present on your own cells).
  
  “Patients receiving a transfusion for the first time do not normally
  have problems with matching blood types and antigens. However it is
  during subsequent transfusions when more care needs to be taken. If,
  during a later transfusion, the blood contains the same antigens as an
  earlier one, the patient’s immune system recognises the transfused
  blood cells as ‘foreign’ and the antibodies (formed after the first
  transfusion) will destroy the blood cells the patient has been given.
  This is called a transfusion reaction and can cause serious illness or
  even death if not treated quickly. That is why matching the blood
  phenotype is so important.”


Now coming to "Why mainly in Middle-East ??"

These rare blood groups are distributed into major 30 discrete system, which mainly  are present in different ethnic groups &amp; communities...mainly living in Middle-Eastern states &amp; Asia...&amp; also in African countries...
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3353626/table/T3/

Intersted people may also check the following articles (or simply search Google)

To Provide Phenotype-Matched Red Blood Cells or Not – That is the Question!

13.3: Pre-transfusion testing- Joint United Kingdom (UK) Blood Transfusion and Tissue Transplantation Services Professional Advisory Committee

&amp; for a complete picture plz browse through- Immunohaematology