title: Prevalence of HLA-B27 in the New Zealand population: effect of age and ethnicity.
abstract: BACKGROUND
  HLA-B27 genotyping is commonly used to support a diagnosis of ankylosing spondylitis (AS). A recent study has suggested that HLA-B27 may adversely affect longevity. The objectives of this study were to determine, for the first time, the prevalence of HLA-B27 in the New Zealand population, and to test whether HLA-B27 prevalence declines with age.
  
  
  METHODS
  117 Caucasian controls, 111 New Zealand Māori controls, and 176 AS patients were directly genotyped for HLA-B27 using PCR-SSP. These participants and a further 1103 Caucasian controls were genotyped for the HLA-B27 tagging single nucleotide polymorphisms (SNPs) rs4349859 and rs116488202. All AS patients testing positive for HLA-B27 of New Zealand Māori ancestry underwent high resolution typing to determine sub-allele status.
  
  
  RESULTS
  HLA-B27 prevalence was 9.2% in New Zealand Caucasian controls and 6.5% in Māori controls. No decline in HLA-B27 prevalence with age was detected in Caucasian controls (p = 0.92). Concordance between HLA-B27 and SNP genotypes was 98.7-99.3% in Caucasians and 76.9-86% in Māori. Of the 14 AS patients of Māori ancestry, 1 was negative for HLA-B27, 10 were positive for HLAB*2705, and 3 positive for HLAB*2704. All cases of genotype discordance were explained by the presence of HLAB*2704.
  
  
  CONCLUSIONS
  HLA-B27 prevalence in New Zealand Caucasians is consistent with that of Northern European populations and did not decline with increasing age. In Māori with AS who were HLA-B27 positive, 76.9% were positive for HLA-B*2705, suggesting that genetic susceptibility to AS in Māori is primarily due to admixture with Caucasians.
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Roberts
authors.forename: Mary C
authors.initials: MC
authors.lastname: Wallace
authors.forename: Gregory T
authors.initials: GT
authors.lastname: Jones
authors.forename: Andre M
authors.initials: AM
authors.lastname: van Rij
authors.forename: Tony R
authors.initials: TR
authors.lastname: Merriman
authors.forename: Andrew
authors.initials: A
authors.lastname: Harrison
authors.forename: Douglas
authors.initials: D
authors.lastname: White
authors.forename: Lisa K
authors.initials: LK
authors.lastname: Stamp
authors.forename: Daniel
authors.initials: D
authors.lastname: Ching
authors.forename: John
authors.initials: J
authors.lastname: Highton
authors.forename: Simon M
authors.initials: SM
authors.lastname: Stebbings
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D005787:Gene Frequency; D020022:Genetic Predisposition to Disease / Q000235:genetics*; D015796:HLA-B27 Antigen / Q000235:genetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009520:New Zealand / Q000453:epidemiology; D020641:Polymorphism, Single Nucleotide; D015995:Prevalence; D013167:Spondylitis, Ankylosing / Q000208:ethnology / Q000235:genetics*; D044465:White People / Q000235:genetics*
chemical_list: C464936:HLA-B*27:05 antigen; D015796:HLA-B27 Antigen