Critical Values

Diagnostic Services: Winnipeg Centre

Diagnostic Services considers certain test results to be “critical values”. Critical result values will be reviewed by the Canadian Blood Services Medical Director / Designate and communicated to the facility nursing unit, responsible nurse and/or responsible physician as appropriate. Whenever possible results shall be sent by fax transmission.

Test Interpretation - Critical Values

Crossmatch Testing

• Positive DAT on a transfusion reaction investigation.
• ABO discrepancy of current sample versus previous record.
• Provision of red cell units that are incompatible but have been approved for issue.
• Unmatched units have been issued and patient was found to have a positive antibody screen upon completion of testing.
• Unmatched units have been issued and are later found to be incompatible upon completion of testing.
• Positive bacterial culture.
• Positive hemoglobin S result obtained post transfusion on IVT and exchange red cell units.

Perinatal Testing

• Positive DAT on cord blood or neonate sample.
• Kleihauer Betke result indicates that >1500 IU of RhIg is required.
• Rh positive mother where the Kleihauer Betke result indicates that a > 30 mL bleed has occurred due to trauma or at full term.
• Antibody titre ≥ 16 in maternal sample.
• Positive Kleihauer Betke result on a mother with an increased AFP.

Platelet Immunology Testing

• Positive HLA antibody screen or HPA antibody on a patient refractory to platelet transfusion
• Positive HPA antibody on maternal NAIT sample or suspected PTP.