Blood Type Testing: Laboratory Orders

Order ABO blood group typing and Rh(D) typing as the essential tests to determine a patient's blood type. 1

Core Laboratory Tests Required

ABO typing determines the presence of A, B, AB, or O antigens on red blood cells and is the most critical test to prevent fatal ABO incompatibility reactions. 1, 2
This test identifies which of the four main blood types (A, B, AB, or O) the patient possesses. 3, 4
ABO typing should be confirmed by reverse grouping, which detects expected isoagglutinins (antibodies) to verify the forward typing results. 2

Rh(D) antigen testing determines whether the patient is Rh-positive or Rh-negative, which is essential for transfusion compatibility and pregnancy management. 1, 2
The Rh(D) antigen is present in approximately 85% of the population. 1
This is particularly important if anti-D immunoglobulin therapy is being considered. 1

The blood sample must be collected and labeled at the patient's bedside with four core identifiers: surname, forename, date of birth, and hospital unique identification number. 1
Positive patient identification is paramount to minimize wrong-blood-in-tube events and risks of ABO incompatibility. 1
The sample must be hand or electronically labeled by appropriately trained personnel at the point of collection. 1

If the patient has received a blood transfusion or been pregnant within the previous 3 months, the sample is only valid for 72 hours (from time of sample collection to subsequent transfusion). 1
Two samples are not always needed if the patient has a suitable historical sample on file with adequate patient identification. 1
For electronic issue of red blood cells, the historical group must have identical patient identification and be transmitted electronically without manual intervention. 1

Extended Rh phenotyping (C, c, E, e antigens) should be performed in patients who may require chronic transfusion support to prevent alloimmunization. 1, 2
The most common Rh phenotypes include DCcee (32.7%), with rare phenotypes like DCCEE occurring in only 0.003% of the population. 5

Kell (K) antigen typing should be considered in patients at risk for alloimmunization, particularly those requiring multiple transfusions. 1, 5
The K antigen is present in approximately 7.5% of the population, while the rare K+k- phenotype occurs in only 0.06%. 5

Blood type and screen (not routine cross-match) should be ordered based on maternal history, anticipated hemorrhagic complications, and local institutional policies rather than as a routine requirement for all patients. 1
A routine blood cross-match is not necessary for healthy and uncomplicated patients undergoing routine procedures. 1

In hemodynamically unstable patients with severe bleeding, blood type and cross-match should be performed immediately to prepare for potential transfusion. 6, 7
For unidentified patients requiring emergency transfusion, use a unique identification system with at least one unique identifier until the patient's identity is confirmed, then collect a new sample with correct patient details. 1

Do not proceed with transfusion if there are any discrepancies between the compatibility label and patient identification—contact the transfusion laboratory immediately. 1
Recognize that weak ABO subgroups (occurring in 0.009% of cases) may require absorption-elution methods or molecular genotyping for accurate determination. 5
Be aware that pseudo-thrombocytopenia due to EDTA-dependent platelet agglutination should be excluded when evaluating complete blood counts. 1