PLHBB - Clinical: Plasma Hemoglobin, Plasma

Test Catalog

Test Name

Test ID: PLHBB    
Plasma Hemoglobin, Plasma

Useful For Suggests clinical disorders or settings where the test may be helpful

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 (ECMO) and centrifugal ventricular assist device (cVAD) patients to assess pump disruption

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Hemoglobin is contained within erythrocytes and significant amounts of "free hemoglobin" (outside the RBC) is not present in plasma in normal states. 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 be present in normal people. 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 red blood cells due to instrumentation, surgical procedures, or mechanical devices. Patients requiring support from extracorporeal membrane oxygenation (ECMO) or centrifugal ventricular assist devices (cVAD) 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 red blood cells. Additionally, bilirubin interferes substantially with the ability to calculate total plasma hemoglobin levels and results in spurious and unreliable results. 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.

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.

TOTAL HEMOGLOBIN

> or =12 months: 0.0-15.2 mg/dL

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

 

OXYHEMOGLOBIN

> or =12 months: 0.0-12.4 mg/dL

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

Interpretation Provides information to assist in interpretation of the test results

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

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

Test should not be performed on serum; hemoglobin is liberated from red blood cells during clotting and will falsely increase the result.

 

Drawing blood specimens for plasma hemoglobin measurement should be done with considerable care to avoid causing hemolysis.

 

Causes of artifactually increased plasma hemoglobin should be excluded and include: forceful aspiration in sample procurement, cannula malposition (high negative-inflow pressures, inadequate pump speed to blood flow ratio), continuous renal replacement therapy, thrombosis or large hematomas.(1)

 

Bilirubin is a known interference with this assay. Elevated bilirubin levels significantly interfere with the quantitation of the total plasma hemoglobin. In the presence of elevated bilirubin (>5 mg/dL), only oxyhemoglobin will be reported. Trending data should be compared within analytes (ie, total hemoglobin to total hemoglobin; and oxyhemoglobin to oxyhemoglobin) as these represent different components in the blood. Therefore, in the presence of bilirubin, the trend can only be compared with baseline oxyhemoglobin levels.

 

If bilirubin is above 5 mg/dL, this comment will be added to the report:

Total plasma hemoglobin not reported due to elevated bilirubin interference. Oxyhemoglobin levels are not affected as significantly by bilirubin levels and are more reliable in this setting. If the plasma hemoglobin test is being utilized in a serial fashion, results should be compared within analyte type (eg, oxyhemoglobin to oxyhemoglobin levels for different time points) and using general trends. Because some variability in this test exists, multiple time points should be used to monitor trends and to confirm wide swings in levels. Because pigmented substances may cause nonspecific interference, clinical correlation is required to establish significance of individual test results.

Clinical Reference Recommendations for in-depth reading of a clinical nature

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

2. Hayes D, 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