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Free Hemoglobin, Plasma

Item Value
Test Update Information The UCSF Clinical Laboratory has identified a problem with the rapid plasma free hemoglobin screening assay involving interfering substances that preclude reporting of specific values for plasma free hemoglobin levels.

Therefore, beginning June 13, 2017 the UCSF Clinical Laboratories will switch from reporting specific values for plasma free hemoglobin to reporting the results qualitatively as follows:
For samples that can be reliably determined to contain a normal level of plasma hemoglobin, the results will reported as "< 8 mg/dL."

For samples that cannot be reliably determined to contain a normal level of plasma hemoglobin, the results will be reported out one of two ways:

1. "Plasma free hemoglobin result may exceed normal cutoff, but does not appear to be above 50 mg/dL. False positive elevations due to interfering substances cannot be ruled out and the precise level of plasma free hemoglobin cannot be determined. Sample sent out for testing by an alternate method."

OR

2. "The level of plasma free hemoglobin cannot be estimated because of possible assay interference. Sample sent out for testing by an alternate method."
Approval req'd? No
Available Stat? Yes
Test code PHGBS
Performed by Parnassus Chemistry
Method HemoCue Plasma/Low Hb Photometer
Collection Instructions Results are highly dependent upon meticulous technique employed in collecting the specimen. To avoid hemolysis use an 18-19 ga. butterfly needle and discard the first 4 mL. Alternatively, apply a tourniquet and perform a venipuncture with an 18-19 ga. needle; collect any other tubes which are needed before releasing the tourniquet with the vacutainer still in the vein and collecting the sample for the hemoglobin assay. If no other samples are being collected at the same time, draw and discard one tube, release the tourniquet, then draw a second tube and submit the second tube for analysis.
Container type Light green top preferred, Dark green top acceptable
Amount to Collect 2 mL blood
Sample type Heparinized plasma
Preferred volume 1 mL plasma
Min. Volume 0.7 mL plasma
Units mg/dL
Normal range < 8 mg/dL
Synonyms hemoglobin, free; Free Hgb; Free Hb
Turn around times STAT 1 hour, Routine 4 hours
Additional information NOTE: This is a rapid test for plasma free hemoglobin with limited analytic sensitivity and low specificity. If a more sensitive and specific test for Plasma Free Hemoglobin is required, please order the sendout test for Plasma Free Hemoglobin (ARUP test code 0020058).

If extreme care is used to avoid hemolysis during phlebotomy and no interfering substances are present, values of <8 mg/dL are normally expected in this assay. Note that this Hemocue assay has been modified to screen for normal levels of Plasma Free Hemoglobin < 8 mg/dL. This rapid assay is susceptible to false positive increases in measured hemoglobin values owing to interfering substances including lipid particles. The sensitivity of the assay is also limited. Therefore, specific values for plasma hemoglobin are not reported including when the results appear to be above the normal cutoff. In cases where the screening results suggest the possibility of an elevated plasma hemoglobin level, the sample will be automatically sent out for independent testing at the ARUP reference laboratory to obtain a specific measurement of the plasma hemoglobin concentration.

For samples that can be reliably determined to contain a normal level of plasma hemoglobin, the results will reported as "< 8 mg/dL."
For samples that cannot be reliably determined to contain a normal level of plasma hemoglobin, the results will be reported out one of two ways:

1. "Plasma free hemoglobin result may exceed normal cutoff, but does not appear to be above 50 mg/dL. False positive elevations due to interfering substances cannot be ruled out and the precise level of plasma free hemoglobin cannot be determined. Sample sent out for testing by an alternate method."
OR
2. "The level of plasma free hemoglobin cannot be estimated because of possible assay interference. Sample sent out for testing by an alternate method."

This test is primarily intended to screen for hemolysis during extracorporeal membrane life support (ECLS) . In patients on ECLS, it is recommended that plasma hemoglobin levels > 50 mg/dL be investigated to determine whether it is being caused by a condition of the patient or by components of the ECLS circuit. See ELSO Guidelines for Cardiopulmonary Extracorporeal Life Support. Extracorporeal Life Support Organization, Version 1:1. April 2009, www.elso.med.umich.edu
To convert mg/dL to µmol/L (SI units) multiply by 0.155.
CPT coding 83051
LOINC code 721-1
Last Updated 6/28/2017 3:58:07 PM
Entry Number 446
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