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Test ID: APOL1 APOL1 Genotype, Varies


Specimen Required


Multiple genotype tests can be performed on a single specimen after a single extraction. See Multiple Genotype Test List in Special Instructions for a list of tests that can be ordered together.

 

Submit only 1 of the following specimens:

 

Specimen Type: Whole blood

Container/Tube: Lavender top (EDTA)

Specimen Volume: 3 mL

Collection Instructions:

1. Invert several times to mix blood.

2. Send specimen in original tube.

Specimen Stability Information: Ambient (preferred) 9 days/Refrigerated 30 days

 

Specimen Type: Saliva

Patient Preparation: Patient should not eat, drink, smoke, or chew gum 30 minutes prior to collection.

Supplies: Saliva Swab Collection Kit (T786)

Specimen Volume: 1 swab

Collection Instructions: Collect and send specimen per kit instructions.

Specimen Stability Information: Ambient 30 days

 

Specimen Type: Extracted DNA

Container/Tube: 2 mL screw top tube

Specimen Volume: 100 mcL (microliters)

Collection Instructions:

1. The preferred volume is 100 mcL at a concentration of 50 ng/mcL.

2. Include concentration and volume on tube.

Specimen Stability Information: Frozen (preferred)/Ambient/Refrigerated


Forms

New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available in Special Instructions:

-Informed Consent for Genetic Testing (T576)

-Informed Consent for Genetic Testing-Spanish (T826)

Useful For

Determining an individual’s APOL1 genotype

 

This test is not useful for clinical management of individuals with APOL1 risk genotypes.

 

This test alone is not useful for determining eligibility for donation or receipt of kidney allografts.(12)

Method Name

Real-Time Polymerase Chain Reaction (PCR) with Allelic Discrimination Analysis

Reporting Name

APOL1 Genotype, V

Specimen Type

Varies

Specimen Minimum Volume

Blood: 0.4 mL
Saliva: 1 swab

Specimen Stability Information

Specimen Type Temperature Time Special Container
Varies Varies

Clinical Information

The APOL1 gene encodes apolipoprotein L-1, a serum apolipoprotein bound to high-density lipoprotein (HDL) particles. Two alleles, commonly called G1 and G2, have been associated with increased risk for development or progression of nondiabetic chronic kidney diseases, including HIV-associated nephropathy (HIVAN), primary focal segmental glomerulosclerosis (FSGS), and lupus-associated collapsing glomerulopathy.(1-4) The G1 allele is a haplotype consisting of 2 missense variants: c.1024A>G (p.Ser342Gly) and c.1152T>G (p.Ile384Met). The G2 allele is comprised of a 6 base pair deletion that results in the deletion of 2 amino acids: c.1164_1169delTTATAA (p.Asn388_Tyr389del). The G1 and G2 alleles are thought to be in complete linkage disequilibrium, meaning when both the G1 and G2 alleles are detected, they are on opposite chromosomes.(1) Risk for chronic kidney disease is only increased when 2 risk alleles are inherited (ie, genotypes G1/G1, G2/G2, or G1/G2), following an autosomal recessive pattern of inheritance.(1) Individuals with one risk allele or no risk alleles do not appear to be at an increased risk.

 

The G1 and G2 risk alleles are enriched in individuals of African ancestry. Population studies show that in individuals of African descent, the G1 allele is found on 20% to 22.5% of chromosomes, and the G2 allele is found on 13% to 15% of chromosomes.(5-6) More importantly, it is estimated that 10% to15% of individuals of African descent carry 2 risk alleles.(5-6) The high frequency of the G1 and G2 alleles in this population is likely due to the protective effect these alleles confer against Trypanosoma rhodesiense, a parasite that causes trypanosomiasis, a disease endemic to Africa.(1) The G1 and G2 alleles are extremely rare or absent in individuals not of recent African descent (eg, European and Asian descent).(1,5) For this reason, increased risk associated with the G1 and G2 alleles has only been stratified in populations of recent African ancestry, and it remains unclear if similar risk effects associated with the APOL1 risk genotypes are applicable to individuals without African ancestry. Currently, there are no guidelines for clinical management of individuals with APOL1 risk genotypes.

 

Evidence exists that the donor APOL1 genotype may impact both donor and recipient outcomes of kidney allografts. Results from 2 studies have shown that donor kidneys from individuals with 2 risk alleles were more likely to fail after transplantation when compared to donor kidneys from individuals with one or no risk alleles.(7-8) Another study suggests that living donors with two risk alleles may be at an increased risk for reduced kidney function following kidney donation.(9) At this time, there has been no association between the genotype of the allograft recipient and transplant outcomes, suggesting that allograft recipients with two risk alleles have similar outcomes to recipients with one or no risk alleles.(10) However, a prospective, large scale study to assess kidney allograft survival from donors with recent African ancestry based on donor and recipient APOL1 genotypes is currently ongoing.(11) Based on presently available data, guidelines advise that an individual’s APOL1 genotype alone should not determine eligibility for donation or receipt of kidney allografts.(12) 

Reference Values

An interpretive report will be provided. 

Interpretation

An interpretive report will be provided.

Clinical Reference

1. Genovese G, Friedman DJ, Ross MD, et al: Association of trypanolytic ApoL1 variants with kidney disease in African Americans. Science. 2010;329(5993):841-845. doi: 10.1126/science.1193032

2. Parsa A, Kao WH, Xie D, et al: APOL1 risk variants, race, and progression of chronic kidney disease. N Engl J Med. 2013;369(23):2183-2196. doi: 10.1056/NEJMoa1310345

3. Kopp JB, Nelson GW, Sampath K, et al: APOL1 genetic variants in focal segmental glomerulosclerosis and HIV-associated nephropathy. J Am Soc Nephrol. 2011;22(11):2129-2137. doi: 10.1681/ASN.2011040388

4. Larsen CP, Beggs ML, Saeed M, Walker PD: Apolipoprotein L1 risk variants associate with systemic lupus erythematosus-associated collapsing glomerulopathy. J Am Soc Nephrol. 2013;24(5):722-725. doi: 10.1681/ASN.2012121180

5. Friedman DJ, Kozlitina J, Genovese G, Jog P, Pollak MR: Population-based risk assessment of APOL1 on renal disease. J Am Soc Nephrol. 2011;22(11):2098-2105. doi: 10.1681/ASN.2011050519

6. Duran CE, Ramírez A, Posada JG, et al: Prevalence of APOL1 risk variants in afro-descendant patients with chronic kidney disease in a Latin American Country. Int J Nephrol. 2019 Dec 18;2019:7076326 doi: 10.1155/2019/7076326

7. Reeves-Daniel AM, DePalma JA, Bleyer AJ, et al: The APOL1 gene and allograft survival after kidney transplantation. Am J Transplant. 2011;11(5):1025-1030. doi: 10.1111/j.1600-6143.2011.03513.x

8. Freedman BI, Julian BA, Pastan SO, et al: Apolipoprotein L1 gene variants in deceased organ donors are associated with renal allograft failure. Am J Transplant. 2015;15(6):1615-1622. doi: 10.1111/ajt.13223

9. Doshi MD, Ortigosa-Goggins M, Garg AX, et al: APOL1 genotype and renal function of black living donors. J Am Soc Nephrol. 2018;29(4):1309-1316. doi: 10.1681/ASN.2017060658

10. Lee BT, Kumar V, Williams TA, et al: The APOL1 genotype of African American kidney transplant recipients does not impact 5-year allograft survival. Am J Transplant. 2012;12(7):1924-1928. doi: 10.1111/j.1600-6143.2012.04033.x

11. Freedman BI, Moxey-Mims MM, Alexander AA, et al: APOL1 long-term kidney transplantation outcomes network (APOLLO): Design and rationale. Kidney Int Rep. 2019;5(3):278-288. doi: 10.1016/j.ekir.2019.11.022

12. Newell KA, Formica RN, Gill JS, et al: Integrating APOL1 gene variants into renal transplantation: Considerations arising from the American Society of Transplantation Expert Conference. Am J Transplant. 2017;17(4):901-911. doi: 10.1111/ajt.14173

Day(s) Performed

Monday through Friday

Report Available

3 to 8 days

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

81479

LOINC Code Information

Test ID Test Order Name Order LOINC Value
APOL1 APOL1 Genotype, V In Process

 

Result ID Test Result Name Result LOINC Value
610559 APOL1 Result In Process
610561 Interpretation 69047-9
610562 Additional Information 48767-8
610563 Method 85069-3
610564 Disclaimer 62364-5
610565 Reviewed by 18771-6
Mayo Clinic Laboratories | Genetics and Pharmacogenomics Catalog Additional Information:

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