American Society for Veterinary Clinical Pathology
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2.8. Crossmatch  


2.8.1. Monitoring – see General recommendations

2.8.2. Method Validation – see General recommendations.

Not all of the method validation experiments listed in section 2.1.2. may be applicable to evaluation of crossmatch methods.  Method validation experiments should be selected or modified as necessary to ensure that new methods/analyzers are functioning satisfactorily to meet the laboratory's requirements and the manufacturer's specifications.

2.8.3. Instrumentation – see General recommendations

2.8.4. Personnel Knowledge – see General recommendations

2.8.5. Quality Control – see also General recommendations

a. Assays

i. A major crossmatch consists of testing patient serum/plasma with a saline suspension of donor red blood cells.

ii. A minor crossmatch, available when donor whole blood has been submitted, consists of testing a saline suspension of patient red blood cells with donor sera/plasma.

b. Recommendations

i. If sera is used for crossmatching, sera should be separated from red blood cells as soon as possible after the sample has clotted.  Samples should be examined for hemolysis and graded with 1+ hemolysis being mild and 4+ hemolysis being severe. Sera (or plasma) samples with 3+ or 4+ hemolysis should be rejected, though more stringent rejection criteria of 1+ hemolysis may be used. Hemolyzed sera/plasma may mask an incompatible hemolytic reaction.  (Lippi, 2006; Giger, pers. Communication) 

ii. Perform patient and donor autocontrols to ensure that reagents, such as diluent, and equipment are functioning properly.  Autocontrols should be handled in parallel with and identical to the major and minor crossmatch samples.

1. Patient autocontrol consists of separated patient serum/plasma and a saline suspension of patient washed red blood cells.

2. When donor whole blood is submitted, the donor autocontrol consists of donor separated sera/plasma and a saline suspension of donor washed red blood cells.

iii. Avoid excessive shaking and tapping, which may yield false negative results by disrupting fragile agglutinates.

iv. Strong rouleaux may mimic true agglutination.  Saline dilution can be performed to disburse rouleaux.

v. False positives may occur secondary to inadequate washing.

vi. Because plasma may contain tiny fibrin clots that may result in pseudoagglutination, false positives may occur when performing crossmatch reactions with plasma.

vii. False negatives may occur secondary to red blood suspensions that are too dilute or too concentrated. 


2.8.6. Procedures Manual – see General recommendations.

Procedures for crossmatch vary with laboratory and species.  Specific protocol recommendations are beyond the scope of these guidelines.  Establishment of crossmatch procedures or adoption from another trusted laboratory is recommended.

2.8.7. Comparison of Tests – see General recommendations

2.8.8. Identification of Out-sourced Tests – see General recommendations