Hemoglobin (Hb), Free, Plasma

CPT: 83051
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Test Details


  • Free Hemoglobin
  • Hb Solubility
  • Hemoglobin, Free
  • Plasma Free Hemoglobin


Evaluate hemolytic anemia, especially intravascular hemolysis. Plasma hemoglobin is increased with intravascular hemolysis, ABO incompatible transfusion, traumatic hemolysis, falciparum malaria, burns, and march hemoglobinuria. Increase may occur in some cases of extravascular hemolysis, delayed transfusion reaction, slight increase in sickle cell anemia, and β-thalassemia.


High (>20 mg/dL) bilirubin, turbidity, methemalbuminemia, lipemic plasma, and hemolysis during or after venipuncture may cause falsely elevated values in the plasma hemoglobin test (method based on peroxide oxidation of TMB).


Based on the catalytic action of hemoglobin on the oxidation of TMB by hydrogen peroxide; rate measured by spectrophotometry

Reference Interval

<5 mg/dL (if conditions are optimal). Values obtained between 5−15 mg/dL should be interpreted with caution since such variables as suboptimal venipuncture may increase results to this range.

Specimen Requirements




1 mL

Minimum Volume

0.1 mL


Green-top (heparin) tube

Patient Preparation

Patient should not exercise just prior to the test.


Recommended procedure for collecting sample without inducing hemolysis: An 18-gauge needle with attached infusion tubing is used. Place the tourniquet lightly around the upper arm. Puncture an antecubital vein with as little trauma as possible. Release the tourniquet and clamp the tubing off as soon as blood return is seen. First collect 3 mL blood in a red-top tube with the rubber top off. Then, collect 5 mL in an anticoagulated tube with the top off. Clamp the tubing, withdraw the needle, and apply a pressure bandage to the site until residual bleeding is stopped. Recap the anticoagulant tube and gently mix three to five times. This specimen is used for the plasma hemoglobin determination. Centrifuge and separate plasma from red cells immediately following collection. To avoid delays in turnaround time when requesting multiple tests on frozen samples, please submit separate frozen specimens for each test requested.

Storage Instructions

Refrigerate at 2°C to 8°C or freeze at -20°C for up to six days.

Stability Requirements



Room temperature

6 days


6 days


6 days

Freeze/thaw cycles

Stable x3

Causes for Rejection

Traumatic venipuncture causing hemolysis; very icteric or lipemic specimen; specimen not heparinized plasma

Clinical Information


A pressure bandage should be applied to the site (following the puncture) to stop residual bleeding.


Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
005595 Hemoglobin, Free, Plasma 721-1 005596 Hemoglobin, Free, Plasma mg/dL 721-1

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