Test ID: REVP
Erythrocytosis Evaluation

The definitive evaluation of an individual with JAK2-negative erythrocytosis associated with lifelong sustained increased RBC mass, elevated RBC count, hemoglobin, or hematocrit

This is a consultative evaluation in which the case will be evaluated at Mayo Medical Laboratories, the appropriate tests performed at an additional charge, and the results interpreted.

For additional information on hemoglobin O2, see Hemoglobin-O2 Affinity p50 Testing (Oxygen Dissociation, p50, Erythrocytes) in Special Instructions.

Also see Erythrocytosis Evaluation Testing Algorithm in Special Instructions

• Hemoglobin-O2 Affinity (P50) Testing (Oxygen Dissociation, P50, Erythrocytes)
• Thalassemia Tests
• Informed Consent for Genetic Testing
• Recommendations for Collection of Control Specimens for P50 and REVP
• Erythrocytosis Patient Information Sheet
• Erythrocytosis Evaluation Testing Algorithm

REV/174: Consultative Interpretation

A2F/83341: Cation Exchange/High-Performance Liquid Chromatography (HPLC)

HBEL/81428: Capillary Electrophoresis

P50/9110: Hemox-Analyzer Measures and Plots O(2) Saturation

IEF/81644: Electrophoresis

MASS/60286: Mass Spectrometry (MS)

HGBMO/29374: Polymerase Chain Reaction (PCR) Analysis/Multiplex Ligation-Dependent Probe Amplification (MLPA), Polymerase Chain Reaction (PCR)/DNA Sequencing

(PCR is utilized pursuant to a license agreement with Roche Molecular Systems, Inc.)

See Recommendations for Collection of Control Specimens for p50 and REVP in Special Instructions.

A total of 3 specimens are required to perform this profile; all 3 specimens must arrive within 72 hours of draw:

-Whole blood EDTA for A2F, HBEL, IEF

-Whole blood sodium heparin for P50*

-Control: Whole blood sodium heparin for P50*

*Please note: If no sodium heparin patient or control specimens are received, the P50 test cannot be performed.

Patient:

Container/Tube: Lavender top (EDTA) and green top (heparin)

Specimen Volume:

EDTA: 5 mL

Heparin: 4 mL

Collection Instructions:

1. Immediately refrigerate specimens after draw.

2. Do not transfer blood to other containers.

3. Rubber band patient specimen and control vial together.

Additional Information: 

1. Patient's age and sex are required.

2. For information on thalassemias and appropriate test ordering, see Thalassemia Tests in Special Instructions.

Forms:

1. New York Clients-Informed consent is required. Please document on the request form or electronic order that a copy is on file. An Informed Consent for Genetic Testing (Supply T576) is available in Special Instructions.

2. Thalassemia/Hemoglobinopathy Information Sheet (Supply T358) is available in Special Instructions.

3. Erythrocytosis Patient Information Sheet (Supply T694) is available in Special Instructions.

4. If not ordering electronically, please submit a Hematopathology/Molecular Oncology Request Form (Supply T241) with the specimen.

Normal Control:

Container/Tube: Green top (heparin)

Specimen Volume: 4 mL

Collection Instructions:

1. Draw a control specimen at the same time from a normal, unrelated, nonsmoking individual.

2. Clearly write normal control on outermost label.

3. Immediately refrigerate specimens after draw.

4. Do not transfer blood to other containers.

5. Rubber band control vial and patient specimen together.

Erythrocytosis (increased RBC mass or polycythemia) may be primary, due to an intrinsic defect of bone marrow stem cells (polycythemia vera: PV), or secondary, in response to increased serum erythropoietin (Epo) levels. Secondary erythrocytosis is associated with a number of disorders including chronic lung disease, chronic increase in carbon monoxide (due to smoking), cyanotic heart disease, high-altitude living, renal cysts and tumors, hepatoma, and other Epo-secreting tumors. When these common causes of secondary erythrocytosis are excluded, a heritable cause involving hemoglobin or erythrocyte regulatory mechanisms may be present.

A less common cause of secondary polycythemia is the presence of a high-oxygen-affinity hemoglobin. Hemoglobins with increased oxygen (O2) affinity commonly result in erythrocytosis caused by an O2 unloading problem at the tissue level. The most common symptoms are headache, dizziness, tinnitus, and memory loss. The affected individuals are plethoric, but not cyanotic. Patients with a high-oxygen-affinity hemoglobin may present with an increased erythrocyte count, hemoglobin concentration, and hematocrit, but normal leukocyte and platelet counts. The p50 and 2,3-bisphosphoglycerate (2,3-BPG, also known as 2,3-DPG) values are low. Changes to the amino acid sequence of the hemoglobin molecule may distort the molecular structure, affecting O2 transport and the binding of 2,3-BPG. 2,3-BPG is critical to O2 transport of erythrocytes because it regulates the O2 affinity of hemoglobin. A decrease in the 2,3-BPG concentration within erythrocytes results in greater O2 affinity of hemoglobin and reduction in O2 delivery to tissues. A few cases of erythrocytosis have been described as being due to a reduction in 2,3-BPG formation. This is most commonly due to mutations in the converting enzyme, bisphosphoglycerate mutase (BPGM). Mutations in the genes EPOR, EPAS1(HIF2A), EGLN1(PHD2), and VHL also cause hereditary erythrocytosis and a subset are associated with subsequent pheochromocytoma and paragangliomas. The prevalence of these mutations is unknown, but they appear less prevalent than mutations that cause high-oxygen-affinity hemoglobin variants, and much less prevalent than polycythemia vera. Because there are many causes of erythrocytosis, an algorithmic and reflexive testing strategy is useful. Initial JAK2 V617F mutation testing and serum Epo levels are important with p50 results further stratifying JAK2-negative cases.

Definitive results and an interpretive report will be provided.

The evaluation includes testing for a hemoglobinopathy and oxygen (O2) affinity of the hemoglobin molecule. An increase in O2 affinity is demonstrated by a shift to the left in the O2 dissociation curve (decreased p50 result).

A hematopathologist expert in these disorders will evaluate the case, appropriate tests are performed, and an interpretive report is issued.

Polycythemia vera and acquired causes of erythrocytosis should be excluded before ordering this evaluation.

1. Patnaik MM, Tefferi A: The complete evaluation of erythrocytosis: congenital and acquired. Leukemia 2009 May;23(5):834-844

2. McMullin MF: The classification and diagnosis of erythrocytosis. Int J Lab Hematol 2008;30:447-459

3. Percy MJ, Lee FS: Familial erythrocytosis: molecular links to red blood cell control. Haematologica 2008 Jul;93(7):963-967

4. Huang LJ, Shen YM, Bulut GB: Advances in understanding the pathogenesis of primary familial and congenital polycythaemia. Br J Haematol 2010 Mar;148(6):844-852

5. Maran J, Prchal J: Polycythemia and oxygen sensing. Pathologie Biologie 2004;52:280-284

6. Lee F: Genetic causes of erythrocytosis and the oxygen-sensing pathway. Blood Rev 2008;22:321-332

7. Merchant SH, Oliveira JL, Hoyer JD, Viswanatha DS: Erythrocytosis. In Hematopathology. Second edition. Edited by ED His. Philadelphia, Elsevier Saunders, 2012, pp 722-723

8. Zhuang Z, Yang C, Lorenzo F, et al: Somatic HIF2A gain-of-function mutations in paraganglioma with polycythemia. N Engl J Med 2012 Sep 6;367(10):922-930

Hemoglobin A2 and F:

Hemolysate of whole blood is injected into an analysis stream passing through a cartridge containing diethylaminoethyl-resin using HPLC. A preprogrammed gradient controls the elution buffer mixture that also passes through the analytical cartridge. The ionic strength of the elution buffer is raised by increasing the percentage of a second buffer. As the ionic strength of the buffer increases the more strongly retained hemoglobins elute from the cartridge. Absorbance changes are detected by a dual-wavelength filter photometer. Changes in absorbances are displayed as a chromatogram of absorbances versus time.(Huismann TH, Scroeder WA, Brodie AN, et al: Microchromotography of hemoglobins. III. A simplified procedure for the determination of hemoglobin A2. J Lab Clin Med 1975;86:700-702; Ou CN, Buffone GJ, Reimer GL, Alpert AJ: High-performance liquid chromatography of human hemoglobins on a new cation exchanger. J Chromatogr 1983;266:197-205)

Hemoglobin Electrophoresis:

The CAPILLARYS System is an automated system that uses capillary electrophoresis to separate charged molecules by their electrophoretic mobility in an alkaline buffer. Separation occurs according to the electrolyte pH and electro-osmotic flow. A sample dilution with hemolysing solution is injected by aspiration. A high-voltage protein separation occurs and direct detection of the hemoglobin protein fractions is at 415 nm, which is specific to hemoglobins. The resulting electrophoregrams peaks are evaluated for pattern abnormalities and are quantified as a percentage of the total hemoglobin present. Examples of position of commonly found hemoglobin fractions are, from cathode to anode: Hb A2', C, A2/O-Arab, E, S, D, G-Philadelphia, F, A, Hope, Bart, J, N-Baltimore, and H.

Oxygen Dissociation, P50:

The operating principle of the Hemox-Analyzer is based on dual wave-length spectrophotometry for the measurement of the oxygen saturation of hemoglobin (in percent) and a Clark electrode for measuring the oxygen partial pressure in millimeters of mercury. The resulting output signals from both measuring systems are fed into a computer, which plots the curve of the resulting function on paper.(Guarnone R, Centenara E, Barosi G: Performance characteristics of Hemox-Analyzer for assessment of the hemoglobin dissociation curve. Haematologica 1995;80:426-430)

IEF Confirms:

Isoelectric focusing: Hemolyzed blood is placed on a polyacrylamide gel containing ampholytes pH 6 to 8. An electrical current is applied to the gel. When hemoglobin (Hb) is in this pH gradient, it moves to its isoelectric point, the pH where its net charge is zero. Once this happens, diffusion is counteracted by the electric field and Hb variants are thus separated as bands at their different isoelectric point.(Hoyer JD, Hoffman DR: The thalassemia and hemoglobinopathy syndromes. In Clinical Laboratory Medicine. Second edition. Edited by KD McMlatchey. Philadelphia, Lippincott Williams and Wilkins, 2002, pp 866-892)

Monday through Friday; Varies

Erythrocytosis Evaluation

82820-Hemoglobin O2 affinity (p50)

83020-Hemoglobin electrophoresis

83021-Hemoglobin A2 and F

82664-IEF confirms

Hemoglobin, Unstable, Blood

83068 (if appropriate)

Hemoglobin Variant by Mass Spectroscopy (MS), Blood

83789 (if appropriate)

Hemoglobin S, Screen, Blood

85660 (if appropriate)

Hemoglobin F, Red Cell Distribution, Blood

88184 (if appropriate)

Hemoglobin Electrophoresis, Molecular

81257 x 2-HBA1/HBA2 (alpha globin 1 and alpha globin 2) (eg, Alpha thalassemia, Hb Bart hydrops fetalis syndrome, HBH disease) gene analysis for common deletions or variant (eg, Southeast Asian, Thai, Filipino, Mediterranean, alpha3.7, alpha4.2, alpha20.5, and Constant Spring) (if appropriate)

81401-HBB (hemoglobin, beta) (eg, sickle cell anemia, hemoglobin C, hemoglobin E), common variants (eg, HbS, HbC, HbE) (if appropriate)

81403-HBB (hemoglobin, beta, beta-globin) (eg, beta thalassemia), duplication/deletion analysis (if appropriate)

81404-HBB (hemoglobin, beta, Beta-Globin) (eg, thalassemia), full gene sequence (if appropriate)

Hereditary Erythrocytosis Mutations

81479-Unlisted molecular pathology procedure

Von Hippel-Lindau (VHL) Gene, Full Gene Analysis

81404-VHL (von Hippel-Lindau tumor suppressor) (eg, von Hippel-Lindau familial cancer syndrome), full gene sequence