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Test ID P50B Oxygen Dissociation, P50, Erythrocytes

Useful For

Identifying hemoglobin variants associated with polycythemia or cyanotic and hypoxic disorders

Profile Information

Test ID Reporting Name Available Separately Always Performed
PINT P50 Interpretation No Yes
P50P Oxygen Dissociation P50 No Yes
CTRL P50 Shipping Control Vial No Yes

Testing Algorithm

See Erythrocytosis Evaluation Testing Algorithm in Special Instructions.

Method Name

Hemox-Analyzer Measures and Plots O2 Saturation

Reporting Name

Oxygen Dissociation P50, RBC

Specimen Type

Control
WB Sodium Heparin


Shipping Instructions


Specimens must arrive within 72 hours of collection.



Necessary Information


Patient's age and sex are required.



Specimen Required


Both a whole blood sodium heparin patient specimen and a control specimen are required as temperature extremes can impact the integrity of the specimen and give falsely altered results.

 

Patient:

Container/Tube: Green top (sodium heparin)

Specimen Volume: 5 mL

Collection Instructions:

1. Immediately refrigerate specimens after collection. Keep at refrigerated temperatures 2 to 8° C. Do not freeze. Freezing causes sample lysis, and tests will not be performed on hemolyzed specimens.

2. Send specimen in original tube. Do not aliquot.

3. Rubber band patient specimen and control vial together. Control must accompany the patient sample at all times to ensure the reliability of testing results.

4. Be sure specimen and control are stored and transported together at refrigerated temperature, carefully following proper handling and shipping instructions.

 

Normal Shipping Control:

Container/Tube: Green top (sodium heparin)

Specimen Volume: 5 mL

Collection Instructions:

1. Draw a control specimen from a normal (healthy), unrelated, nonsmoking person at the same time as the patient.

2. Handwrite "normal control" clearly on the outermost label.

3. Immediately refrigerate specimen after collection. Keep at refrigerated temperatures 2 to 8° C. Do not freeze.

4. Send specimen in original tube. Do not aliquot.

5. Rubber band patient specimen and control vial together. Control must accompany the patient sample at all times to ensure the reliability of testing results.


Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time
Control Refrigerated 72 hours
WB Sodium Heparin Refrigerated 72 hours

Reject Due To

Hemolysis

Mild reject; Gross reject

Lipemia

NA

Icterus

NA

Other

No control vial sent, lithium heparin tube

Clinical Information

Abnormal oxygen affinity is demonstrated in the presence of some hemoglobin variants:

-High oxygen affinity causes erythrocytosis

-Low oxygen affinity causes cyanosis and/or low oxygen saturation.

 

Increased oxygen affinity of hemoglobin, reflected in a low p50, left-shifted oxygen dissociation curve, and loss of normal sigmoidal configuration, are characteristic of many hemoglobin variants that are responsible for polycythemia. Measurement of oxygen affinity is an important method for diagnosis of these disorders.

Reference Values

≥12 months: 24-30 mm Hg

Reference values have not been established for patients who are <12 months of age.

Interpretation

Normal: p50 =24 to 30 mm Hg (with sigmoidal oxygen dissociation curve)

 

An interpretive report will be provided

Cautions

To ensure valid results, the specimen must be ≤72 hours old.

 

Resulting Cautions:

P50 results will be reported if the shipping control is normal. The shipping control is necessary for ensuring valid results. If the specimen is compromised, such as during transport, this often results in an abnormal result in both the control and specimen.

 

If the shipping control is abnormal and the p50 results are within normal range, the results will be reported; however, a comment will be added to the report indicating that the shipping control was not entirely satisfactory.

 

The test will be cancelled if the patient specimen and shipping control are both abnormal.

Clinical Reference

Beutler E: Polycythemia. In Williams Hematology. Sixth edition. Edited by E Beutler, MA Lichtman, BS Coller, TJ Kipps. New York, McGraw-Hill Book Company, 2001, pp 689

Day(s) and Time(s) Performed

Monday through Sunday

Analytic Time

1 day

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

82820

LOINC Code Information

Test ID Test Order Name Order LOINC Value
P50B Oxygen Dissociation P50, RBC In Process

 

Result ID Test Result Name Result LOINC Value
37951 P50 Shipping Control Vial No LOINC Needed
37950 Oxygen Dissociation P50, RBC 65343-6
37949 P50 Interpretation 59466-3

NY State Approved

Yes

Forms

If not ordering electronically, complete, print, and send a Benign Hematology Test Request (T755) with the specimen.