121363: Hemoglobinopathy Fractionation Cascade With Reflex to α-Thalassemia

Test Details

Methodology

CBC: Automated cell counter; ferritin: electrochemiluminescence immunoassay (ECLIA); hemoglobin fractionation cascade: capillary electrophoresis (CE), high-pressure liquid chromatography (HPLC); hemoglobin solubility: sodium hydrosulfite reduction

If reflexed to a-thalassemia DNA test: polymerase chain reaction (PCR) and multiplex ligation-dependent probe amplification (MLPA)

Alpha-globin variants included in the analysis are the Constant Spring non-deletion variant and the following deletions: -alpha3.7, -alpha4.2, --alpha20.5, --SEA, --FIL, --THAI, --MED, and the HS-40 regulatory region

CBC: Automated cell counter; ferritin: electrochemiluminescence immunoassay (ECLIA); hemoglobin fractionation cascade: capillary electrophoresis (CE), high-pressure liquid chromatography (HPLC); hemoglobin solubility: sodium hydrosulfite reduction; if reflexed to α-thalassemia: polymerase chain reaction (PCR) and gel electrophoresis.

If reflexed to a-thalassemia DNA test: polymerase chain reaction (PCR) and multiplex ligation-dependent probe amplification (MLPA)

Result Turnaround Time

4 - 8 days

Turnaround time is defined as the usual number of days from the date of pickup of a specimen for testing to when the result is released to the ordering provider. In some cases, additional time should be allowed for additional confirmatory or additional reflex tests. Testing schedules may vary.

Test Includes

Complete blood count (CBC) without differential; ferritin; hemoglobinopathy fractionation cascade profile; reflex to α-thalassemia DNA testing for variants in the HBA1 and HBA2 genes when appropriate (see Use)

Complete blood count (CBC) without differential; ferritin; hemoglobinopathy fractionation cascade profile; reflex to α-thalassemia ~~when appropriate. (See Special Instructions.~~)

Use

This test is used to diagnose for alpha thalassemia and hemoglobin variants, with ferritin to evaluate total body storage iron and complete blood count without differential to detect and/or identify a wide range of hematologic disorders. When appropriate, additional reflex testing will be performed for alpha-thalassemia DNA analysis of the a-globin gene locus (HBA1/HBA2 OMIM 141800 and 141850,16pter-16p13.3). This analysis includes seven common alpha-thalassemia deletions (alpha-3.7, alpha-4.2, SEA, MED, THAI, FIL, and a-(20.5)), as well as the Constant Spring variant and the HS-40 regulatory region. Refer to individual assays for additional information.

Diagnose thalassemias and hemoglobin variants, with ferritin to evaluate total body storage iron, and complete blood count without differential to detect and/or identify a wide range of hematologic disorders. When appropriate, additional reflex testing will be performed for α-thalassemia. DNA analysis of the α-globulin gene locus (HBA1/HBA2 OMIM 141800 and 141850,16pter-16p13.3) can detect copy-number changes by targeting 24 different sequences in the α-globulin region, and will, in principle, detect all genomic deletions and duplications involving this locus, in addition to the Constant Spring point mutation. The mutations analyzed include Southeast Asian(--SEA), Thai(--Thai), Filipino(--FIL), Mediterranean(--MED), a3.7, and a4.2.

Special Instructions

This test is intended for adults age 20 and older. If MCV is <80 and ferritin is normal or high, testing will reflex to alpha-thalassemia DNA (α-Thalassemia Analysis [484278]). If reflex testing is performed, additional charges/CPT code(s) will apply.

Hemoglobinopathy fractionation may exhibit interference when sample is collected from a person who is consuming a supplement with a high dose of biotin (also termed as vitamin B7 or B8, vitamin H, or coenzyme R). It is recommended to ask all patients who may be indicated for this test about biotin supplementation. Patients should be cautioned to stop biotin consumption at least 72 hours prior to the collection of a sample.

This test is intended for adults age 20 and older. If MCV is <80 and ferritin is normal or high, testing will reflex to ~~α-thalassemia DNA. If reflex test is performed, additional charges/CPT code(s) may apply.~~

This test may exhibit interference when sample is collected from a person who is consuming a supplement with a high dose of biotin (also termed as vitamin B7 or B8, vitamin H, or coenzyme R). It is recommended to ask all patients who may be indicated for this test about biotin supplementation. Patients should be cautioned to stop biotin consumption at least 72 hours prior to the collection of a sample.

Limitations

Limitations for ferritin: As with all tests containing monoclonal mouse antibodies, erroneous findings may be obtained from samples taken from patients who have been treated with monoclonal mouse antibodies or have received them for diagnostic purposes.¹ In rare cases, interference due to extremely high titers of antibodies to streptavidin and ruthenium can occur.¹ The ferritin test contains additives that minimizes these effects.

Limitations for reflex DNA test: Technologies used do not detect germline mosaicism and do not rule out the presence of large chromosomal aberrations including rearrangements and gene fusions, or variants in regions or genes not included in this test, or possible inter/intragenic interactions between variants or repeat expansions. Variant classification and/or interpretation may change with time if more information becomes available. False positive or false negative results may occur for reasons that include: rare genetic variants, sex chromosome abnormalities, pseudogene interference, blood transfusions, bone marrow transplantation, somatic or tissue-specific mosaicism, mislabeled samples or erroneous representation of family relationships.

This test was developed and its performance characteristics determined by Labcorp. It has not been cleared or approved by the Food and Drug Administration.

Limitations for Ferritin: As with all tests containing monoclonal mouse antibodies, erroneous findings may be obtained from samples taken from patients who have been treated with monoclonal mouse antibodies or have received them for diagnostic purposes.¹ In rare cases, interference due to extremely high titers of antibodies to streptavidin and ruthenium can occur.¹ The ferritin test contains additives that minimizes these effects.

This test was developed and its performance characteristics determined by Labcorp. It has not been cleared or approved by the Food and Drug Administration.

Custom Additional Information

Refer to individual assays for additional information.

Specimen Requirements

Specimen

Whole blood and serum

Volume

Three lavender-top (EDTA whole blood) tubes filled to capacity and 0.8 mL serum

Minimum Volume

Two lavender-top (EDTA whole blood) tubes filled to capacity and 0.3 mL serum. (Note: This volume does not allow for repeat testing.)

Container

Lavender-top (EDTA) tubes and red-top tube or gel-barrier tube

Collection Instructions

Lavender-top (EDTA) tubes should be filled to capacity and inverted 8 to 10 times immediately after tube is filled, at the time of collection. If a red-top tube is used for serum, transfer separated serum to a plastic transport tube.

Stability Requirements

Temperature	Period
Room temperature	Serum ferritin: 14 days; whole blood CBC: 1 day; whole blood Hgb fractionation: 14 days; whole blood for reflex DNA test: 14 days
Refrigerated	Serum ferritin: 14 days; whole blood CBC: 3 days; whole blood Hgb fractionation: 14 days; whole blood for reflex DNA test: 30 days
Frozen	Serum ferritin: 14 days; whole blood CBC: unstable; whole blood Hgb fractionation: 14 days
Freeze/thaw cycles	Serum ferritin: stable x3; whole blood CBC: unstable; whole blood Hgb fractionation: stable x3

Temperature

Period

Room temperature

Serum ferritin: 14 days; Whole blood CBC: 1 day; Whole blood Hgb fractionation: 14 days

Refrigerated

Serum ferritin: 14 days; Whole blood CBC: 3 days; Whole blood Hgb fractionation: 14 days

Frozen

Serum ferritin: 14 days; Whole blood CBC: Unstable; Whole blood Hgb fractionation: 14 days

Freeze/thaw cycles

Serum ferritin: Stable x3; Whole blood CBC: Unstable; Whole blood Hgb fractionation: Stable x3

Temperature	Period
Room temperature	Serum ferritin: 14 days; whole blood CBC: 1 day; whole blood Hgb fractionation: 14 days; whole blood for reflex DNA test: 14 days
Refrigerated	Serum ferritin: 14 days; whole blood CBC: 3 days; whole blood Hgb fractionation: 14 days; whole blood for reflex DNA test: 30 days
Frozen	Serum ferritin: 14 days; whole blood CBC: unstable; whole blood Hgb fractionation: 14 days
Freeze/thaw cycles	Serum ferritin: stable x3; whole blood CBC: unstable; whole blood Hgb fractionation: stable x3

Storage Instructions

Serum ferritin: room temperature

Whole blood CBC: room temperature up to 24 hours

Whole blood for reflex DNA test: Maintain specimen at room temperature or refrigerate at 4°C. Do not freeze.

Whole blood Hgb fractionation: refrigerated

~~Serum ferritin: Room temperature~~

Whole blood CBC: Room temperature up to 24 hours

Whole blood Hgb fractionation: Refrigerated

Serum ferritin: room temperature

Whole blood CBC: room temperature up to 24 hours

Whole blood for reflex DNA test: Maintain specimen at room temperature or refrigerate at 4°C. Do not freeze.

Whole blood Hgb fractionation: refrigerated

Causes for Rejection

Hemolysis; quantity not sufficient for analysis; tube not filled with minimum fill volume; specimen drawn in anticoagulant other than EDTA; specimen diluted or contaminated with IV fluid; clotted specimen; improper labeling; transfer tubes with whole blood; lavender-top (EDTA) tubes received with plasma removed; frozen specimens

References

Tamary H, Dgany O. Alpha-Thalassemia. Adam MP, Feldman J, Mirzaa GM, Pagon RA, Wallace SE, Amemiya A, editors. In: GeneReviews^® [Internet]. Seattle (WA): University of Washington, Seattle; 1993. 2005 Nov 1 [updated 2024 May 23]. PubMed 20301608

Footnotes

1. Ferritin. V7 Elecsys and Cobas Analyzers [package insert]. Indianapolis, IN: Roche; 2007-2008.

1. Ferritin. V7 Elecsys and Cobas Analyzers [package insert]. Indianapolis, IN: Roche; 2007-08.