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Test ID: PLHBB Plasma Free Hemoglobin, Plasma

Reporting Name

Plasma Free Hemoglobin, P

Useful For

Determining whether hemolysis is occurring such as from:

-Transfusion reaction

-Mechanical fragmentation of red blood cells

-Relative comparison to baseline levels in extracorporeal membrane oxygenation and centrifugal ventricular assist device patients to assess pump disruption

Specimen Type

Plasma EDTA

Specimen Required

Collection Container/Tube: Lavender top (EDTA)

Submission Container/Tube: Plastic vial

Specimen Volume: 2 mL

Collection Instructions:

1. Centrifuge and transfer plasma to a plastic vial within 2 hours of collection.

2. Results could be falsely elevated due to artifactual red blood cell lysis if not centrifuged within 2 hours of collection.

Specimen Minimum Volume

1.5 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Plasma EDTA Refrigerated (preferred) 20 days
  Frozen  30 days
  Ambient  4 days

Reference Values


≥12 months: 0.0-15.2 mg/dL

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



≥12 months: 0.0-12.4 mg/dL

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

Day(s) Performed

Monday through Sunday

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 US Food and Drug Administration.

CPT Code Information


LOINC Code Information

Test ID Test Order Name Order LOINC Value
PLHBB Plasma Free Hemoglobin, P 87433-9


Result ID Test Result Name Result LOINC Value
31970 Total Plasma Hemoglobin 721-1
31971 Oxyhemoglobin 87437-0

Clinical Information

Hemoglobin is contained within erythrocytes and significant amounts of "free hemoglobin" (outside the red blood cell [RBC]) are not normally present in plasma. This free hemoglobin is also called plasma hemoglobin.


Normal blood draw procedures cause a limited degree of unavoidable disruption and therefore a small amount of free hemoglobin may normally be present. When detectable, the total plasma hemoglobin and a subcomponent, oxyhemoglobin, are both reported.


Significant amounts of free hemoglobin occur in plasma following disruption of the RBC for any reason. This might result from a transfusion reaction or mechanical fragmentation of RBCs due to instrumentation, surgical procedures, or mechanical devices. Patients requiring support from extracorporeal membrane oxygenation or centrifugal ventricular assist devices are commonly monitored for trends in plasma free hemoglobin levels to assess for increasing hemolysis. Sharp spikes in plasma hemoglobin levels can indicate pump disruption. However, plasma hemoglobin can be artifactually increased due to a traumatic blood draw or prolonged exposure to post-draw RBCs. Additionally, bilirubin interferes substantially with the ability to calculate total plasma hemoglobin levels and results may be spurious and unreliable. This is a difficulty frequently encountered in serially tested patients. When this occurs, the oxyhemoglobin level tends to show less interference and will be the only analyte reported in the presence of increased bilirubin (>5 mg/dL). When using trending data, total plasma hemoglobin and oxyhemoglobin levels are not interchangeable and should be compared within their subgroups only.


An elevation in plasma hemoglobin above the reference range indicates likely intravascular hemolysis due to one of the causes listed in the Useful For section.

Clinical Reference

1. Lubnow M, Philipp A, Foltan M. et al: Technical complications during veno-venous extracorporeal membrane oxygenation and their relevance predicting a system-exchange-retrospective analysis of 265 cases. PloS One. 2014 Dec 2;9(12):e112316

2. Hayes D Jr, McConnell PI, Preston TJ, Nicol KK: Hyperbilirubinemia complicating plasma-free hemoglobin and antifactor Xa level monitoring on venovenous extracorporeal membrane oxygenation. World J Pediatr Congenit Heart Surg. 2014 Apr;5(2):345-347

Report Available

1 to 3 days

Method Name

Spectrophotometry (SP)


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

Mayo Clinic Laboratories | Hematology Catalog Additional Information: