What test should be ordered to check blood type in an outpatient setting?

Blood Type Testing in the Outpatient Setting

Order an ABO/Rh blood type and screen (also called "Type and Screen") which includes ABO blood group, Rh(D) antigen, and antibody screening for irregular antibodies.

Standard Test Components

The standard outpatient blood typing order should include:

• ABO blood group determination (A, B, AB, or O) using both forward typing (testing patient RBCs with anti-A and anti-B antibodies) and reverse typing (testing patient serum for expected isoagglutinins) 1
• Rh(D) antigen testing to determine Rh positive or negative status 1
• Antibody screening to detect unexpected antibodies against RBC antigens, which is critical for future transfusion safety 1, 2

Ordering Terminology

The test is typically ordered as:

• "Type and Screen"
• "ABO/Rh with antibody screen"
• "Blood type and antibody screen"

This is the standard pretransfusion testing panel that provides comprehensive blood group information 2.

Extended Typing Considerations

For patients with specific clinical needs (sickle cell disease, anticipated multiple transfusions, or pregnancy), order extended RBC antigen phenotyping beyond ABO/Rh:

• Extended phenotype should include C, c, E, e (Rh antigens) and K (Kell antigen) at minimum 3
• This can be ordered as "extended RBC phenotype" or "extended antigen typing" 3
• Genotyping is preferred over serologic phenotyping when available, as it provides more accurate results and additional antigen information, particularly if the patient has been transfused within 3 months 3

Critical Timing Considerations

• Sample validity is 72 hours if the patient has been transfused or pregnant within the previous 3 months 3
• For patients without recent transfusion or pregnancy, a historical sample may be valid for comparison, but current standards require proper patient identification verification 3
• Blood samples must be collected and labeled at the patient's bedside with at least two unique identifiers (surname, forename, date of birth, and hospital/NHS number) 3

Common Pitfalls to Avoid

• Do not order just "ABO typing" alone - this misses critical antibody screening that could identify alloantibodies causing future transfusion reactions 1
• Avoid testing immediately after transfusion - recent transfusion creates chimerism with donor RBCs circulating, which can confuse results 4
• Be aware that certain medications (particularly daratumumab used in multiple myeloma) significantly complicate blood typing and require specialized laboratory techniques 4
• Weak ABO subgroups (occurring in approximately 0.009% of population) may require additional absorption-elution methods or molecular genotyping for accurate determination 5

Special Populations

For patients with bleeding disorders being evaluated, ABO blood group is performed by 70% of specialists as part of first-line testing because blood type O is associated with lower von Willebrand factor levels, which can affect bleeding risk assessment 6.