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Abstract: PO1638

The Distribution of APOL1 Risk Variants and Their Association with CKD in Rural East Africa: The SEARCH-CKD Study

Session Information

Category: Genetic Diseases of the Kidneys

  • 1002 Genetic Diseases of the Kidneys: Non-Cystic

Authors

  • Muiru, Anthony N., University of California San Francisco, San Francisco, California, United States
  • Elly, Assurah Wandago, Kenya Medical Research Institute, Nairobi, Kenya
  • Kabami, Jane, Infectious Diseases Research Collaboration, Kampala, Central Region, Uganda
  • Atukunda, Mucunguzi, Infectious Diseases Research Collaboration, Kampala, Central Region, Uganda
  • Chan, Wendy, University of California San Francisco, San Francisco, California, United States
  • Puck, Jennifer, University of California San Francisco, San Francisco, California, United States
  • Charlebois, Edwin, University of California San Francisco, San Francisco, California, United States
  • Havlir, Diane, University of California San Francisco, San Francisco, California, United States
  • Kamya, Moses, Infectious Diseases Research Collaboration, Kampala, Central Region, Uganda
  • Estrella, Michelle M., University of California San Francisco, San Francisco, California, United States
  • Hsu, Chi-yuan, University of California San Francisco, San Francisco, California, United States
Background

Apolipoprotein L1 (APOL1) high-risk genotypes (G1/G1, G1/G2 or G2/G2) are well-known CKD risk factors that arose in sub-Saharan Africa. The G1 and G2 allele frequencies may be as high as 45% and 24%, respectively in some West African countries, but few studies have examined the association of high-risk genotypes and CKD in Eastern Africa.

Methods

We conducted a study of CKD prevalence among a population-based sample of 3,686 participants (PMC7055898) nested within an HIV trial in rural Uganda and Kenya. We collected dried blood spots (DBS) on filter cards for subsequent genetic studies. After DNA extraction, we genotyped APOL1 risk variants and used multivariable logistic regression models to assess the association of APOL1 high-risk genotypes with prevalent CKD defined as a serum creatinine-based eGFR <60 mL/min/1.73m2 or proteinuria (urine dipstick ≥1+).

Results

We successfully obtained DBS from 90% of all individuals approached for the study. We have extracted DNA and genotyped 492 (~10%) samples (convenient selection). Un-weighted CKD prevalence among these individuals was 7.7% (95% CI: 5.2-11%). The overall allele frequencies for APOL1 G1 and G2 variants were 6.1% and 5.8%, respectively and varied by region (Figure 1). Only 2.2% of individuals had APOL1 high-risk genotypes. The adjusted odd ratio for association of APOL1 high-risk genotypes with CKD was 1.5 (95% CI 0.15-15) in this limited sample.

Conclusion

Our study is one of the largest studies to define the prevalence of APOL1 risk variant frequencies and evaluate the association of APOL1 high risk genotype with CKD in rural East Africa. Our preliminary results show a relatively low prevalence of APOL1 risk variants—supporting the distinctive west-east Africa cline in APOL1 distribution previously reported. Further genotyping will permit more precise estimation of the association of APOL1 and CKD.

APOL1 risk variant frequencies by study region

Funding

  • NIDDK Support