type and screen ( t&s ) , done pre - operatively to prevent complications from blood transfusion incompatibility between donor and recipient for existence of alloantibody .
alloantibody screening is a laboratory method for detection of broad range unexpected ( usually clinically significant , igg ) an antibody(s ) against an antigen(s ) ( usually the minor blood group ) in sample sera that blood recipient lacks . indeed
if the blood recipient recognizes the donor rbc surface antigens as foreign , the host will mount an immune response to the donor rbc s .
those unexpected antibodies are usually results of rbcs stimulation including history of blood transfusion , pregnancy or history of miscarriage .
although , naturally occurring alloantibody(s ) may be present in some patient sample . clinically significant alloantibody(s ) affected by igg immunoglobulin could be associated with hemolytic disease of new born ( hdn ) , hemolytic transfusion reaction ( htr ) and notable decreases in the survival of transfused rbcs . according to similar studies , the prevalence of clinically significant alloantibodies has been reported from less than 0.5% to up to 60% of samples depending on the population study and the test method sensitivity , while in those patients receiving blood products regularly consisting of patients suffering from different type of malignancy , hemoglobinopathies or hematological disorders the rate of unexpected antibodies is significantly higher compared to those patients underwent elective surgery or those women had a history of pregnancy or miscarriage .
this procedure ( t&s ) is much reliable and even less expensive than full cross matching and gives the same immunohematological safety . in the t&s test , each recipient s blood sample is typed for its abo and rh d blood groups and screened for unexpected but clinically significant antibody(s ) that could to lead to red blood cell ( rbcs ) alloimmunization .
the recipient s serum is incubated with two or three different group - o screening red cells ( not pooled ) in 2 - 5% rbcs suspension , which carry important and representative blood group antigens as homozygote including d , c , e , c , e , m , n , s , s , p1 , lea , leb , k , k , fya , fyb , jka , and jkb antigens .
it is one of the most important complications of blood transfusions . in the presence of alloantibody ,
the life span of red blood cells is shortened and the patient s need for blood increases .
identification of the types of antigens present and transfusion of fully compatible blood may prevent alloimmunization . 
 
so , in this study , we evaluated relative frequencies of alloantibody against rbc in a general population of ardabil , ( ardabil province in north west of iran with azeri race ) whose referred to imam khomeini hospital for elective surgery and may be candidate to receive blood transfusion .
in this cross - sectional study , type and screen test done as a pre - transfusion test for 1420 patients of imam khomeini hospital in ardabil that underwent elective surgery between march 2012 and february 2013 .
blood group typing done by anti - a , anti - b and anti - d reagent ( iranian blood research and fractionation holding company , tehran - iran ) in tube test procedure for each patient .
screening test , also done by antibody screening kit contains three vials of rbc with known surface antigen ( iran blood transfusion organization , iran , lot no : 11ip3c40 - 13ip3c65 ) according to manufactory method in room temperature and 37c .
briefly , add 2 drops of patient plasma / serum to be tested to each labeled tube .
then , add one drop of thoroughly mixed reagent red cells to the appropriate labeled tube . afterwards , 2 drops of albumin 22% added to each tube . after mixing the contents of each tube ,
incubate all tubes at room temperature and 37c ( 1c ) for 10 - 30 minutes . then proceed directly with the antiglobulin test phase following incubation .
immediately re - suspend the cells by gentle agitation ; examine the tubes macroscopically for agglutination .
patients with positive results ( presence of antibody in their serum ) continued by antibody identification test ( iran blood organization , iran , lot no : 11ip11c40 - 13ip11c65 ) .
this kit contains 11 cell panels and had a similar method to antibody screening test ( described above ) .
dat ( direct anti - globulin test ) done for patients with positive auto - control .
in this study , of 1420 patients , 842 ( 59.3% ) were male and 578 ( 40.7% ) were female .
patient s age ranged between 5 and 82 year and had mean age of 43.2  24.7 year .
prevalence of alloantibody in this population was 0.92% ( 13 patients ) and 99.2% ( 1407 patients ) showed no alloantibody in their serum .
of 13 alloimmunized patients , 7 patients ( 8% of male population ) were male and 6 patients ( 1% of female population ) were female .
there was not any significant relationship between sex and prevalence of alloantibody ( p > 0.05 ) .
the identified antibodies contains : k , e , c , lea , c , fya and d ( table 1 ) .
anti - k and anti- lea , was the most prevalent clinical significant , and non - significant antibodies , respectively .
the mean age of alloimmunized group was 45.2 year and in non - alloimmunized group had mean age of 43.8 year .
no significant correlation found between age and prevalence of alloantibody among patients ( p > 0.05 ) . 
 
prevalence of alloantibody among patients ready to elective surgery of total 1420 under study patients , 1318 patients ( 93% ) had no history of blood transfusion and 7% of patients had blood transfusion in past . among patients with positive antibody screening test , 10 patients had history of blood transfusion and a significant relationship found between history of transfusion and alloimmunization ( p < 0.05 ) . during the study , observed that demands for reservation of blood reduces significantly than before establishment of ts policy ( p < 0.05 ) .
a reason for this assurance is the successful use of maximum surgical blood order schedules , which guide clinicians and blood banks alike in predicting the number of units that will need to be prepare for commonly performed surgical procedures .
after the introduction of the indirect anti - globulin test by coombs in 1945 , which added a new dimension to the safety of blood transfusion , there was a rapid increase in the identification of alloantibody that caused transfusion reactions or hemolytic disease of the newborn .
this includes rbc antigenic difference between the blood donor and the recipient , the recipient s immune status and immunomodulatory effect of the allogenic blood transfusions on the recipient s immune system . in our study ,
prevalence of alloantibody was 0.9% . in a study conducted in minnesota region on normal population between 1975 and 1995 ,
the rate of prevalence of alloantibody against red cell antigens was less than one percent .
the most prevalent antibody was against e , le and k antigens , respectively . in another study in tehran ( central part of iran ) between 1997 and 1998 ,
these efforts beside our study data and more similar reports in worldwide indicated that in normal population , incidence of occurrence of alloimmunization is less than one percent .
history of blood transfusion and pregnancy can lead to formation of alloantibody . beside alloantibody ,
also autoantibody can be a source of potential risk in blood transfusion and must be regarded in antibody screening tests . in our study , we did not find any correlation between formation of alloantibody and gender .
like our study in similar study in tehran , also no relationship found between gender and prevalence of alloantibody . while , in a study in kuwait occurrence of alloantibody was higher in females .
, in our study , antibody against k , e and c antigens with 30% , 15% and 15% prevalence , respectively , had higher rate among the other rbc antigens .
in western europe and the united states , the most frequently reported alloantibody in alloimmunized patients were alloantibody against rh and kell antigens . in a study in minnesota , also anti - e and anti - k had higher rate than the other .
prevalence of a specific antigen in region under study and also application of different methods and reagents can be considered as an explanation for this difference .
alloantibody against these antigens has ability to mediate an intermediate to strong hemolytic reaction in recipients .
thus , identification of these antigens in donors associated with precise performance of antibody screening and antibody identification tests have a significant role in reducing the risk of a hemolytic reaction . in our study , as expected , history of blood transfusion has a direct correlation with production of alloantibody especially in males , because women due to pregnancy have higher ability to produce alloantibody than men .
the t&s test provides many benefits to patients and the main one is that , blood issued is safe and compatible . in cross - match test , blood units are randomly tested without information about the patient s antibody status . for cross - match test , blood units must reserve for a designated patient and this led to overestimate the number of units that would be required .
in addition , as a repeat cross - match required at least another 1 to 2 hours and increase the workload of the blood bank staff . by t&s test , blood units are no longer reserved for a patient if the results from the antibody screen are negative and instead , a validity period is given to an individual for their negative antibody screen status .
therefore , alloantibody screening must to preformed for patients needing blood transfusion , pregnant women , cases of blood cells transfusion reactions by blood bank laboratory in hospitals and finally for blood and plasma donors by blood transfusion establishments .
 introductionalloimmunization is a reaction of the immune system to foreign antigens . for prevention of alloantibody formation , 
 performing of type and screen test is necessary on a patient s blood specimen as part of pre - transfusion testing.materials and methodin this cross - sectional study , type and screen test done for 1420 patients with elective surgery for detection of alloantibody in imam khomeini hospital in ardabil.resultsprevalence of alloantibody in this population was 0.92% ( 13 patients ) and 99.2% ( 1407 patients ) showed no alloantibody in their serum . 
 the most prevalent alloantibody was anti - k , anti - e and anti - c . 
 no significant relationship observed between sex and alloimmunization rate.conclusionperformance of type and screen test play an important role in reducing the rate of alloimmunization , and also , could reduce the demands for blood reservation in hospital blood banks . 
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
CONCLUSION