Test ID: P50
Oxygen Dissociation, P50, Erythrocytes
Useful For 
Suggests clinical disorders or settings where the test may be helpful
Identifying hemoglobin variants associated with polycythemias
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Abnormal oxygen affinity is demonstrated in the presence of some hemoglobin variants:
-High oxygen affinity causes erythrocytosis
-Low oxygen affinity causes cyanosis
Increased oxygen affinity of hemoglobin, reflected in a low p50, left-shifted oxygen dissociation curve, and loss of normal sigmoidal configuration, is characteristic of many hemoglobin variants that are responsible for polycythemia. Measurement of oxygen affinity is the most important method for diagnosis of these disorders.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
24-30 mm Hg
Interpretation Provides information to assist in interpretation of the test results
Normal: p50=24mm Hg to 30 mm Hg (with sigmoidal O2 dissociation curve)
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
To ensure valid results, the specimen must be < or =72 hours old.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
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, p 689
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