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P 50 Calculated
Test CodeP50
Alias/See Also
none
CPT Codes
82820
Includes
p50 calculation, pH (venous), pO2 (venous), O2 Saturation (venous), Methemoglobin, Carboxyhemoglobin
Preferred Specimen
Heparinized venous blood
Minimum Volume
1 mL
Other Acceptable Specimens
none
Transport Container
Lithium Heparin (green top) tube
Transport Temperature
On ice or refrigerated
Specimen Stability
On ice - 1 hour; Refrigerated - 24 hours
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Clotted samples, frozen, expired stability time
Methodology
Potentiometry
Setup Schedule
Daily upon receipt
Report Available
Upon completion of analysis
Reference Range
P50: 22.6 - 29.4 mm Hg
pH (venous): 7.32 - 7.42
Methemoglobin: 0.4 - 1.5%
Clinical Significance
Measuring the strength of oxygen binding to hemoglobin at standard in-vitro conditions is of clinical importance because it is a means of detecting the presence of a mutant hemoglobin with high or low affinity for oxygen. Hemoglobins with markedly altered affinity for oxygen may be the cause of polycythemia or, less commonly, anemia.