In a recently published study1 involving 79 ankylosing spondylitis (AS) patients and 132 unrelated healthy blood donors, Zhu et al report association of a tumour necrosis factor α (TNFα) single nucleotide polymorphism (SNP), rs1799724, with AS.1 I have many concerns with this paper and its conclusions.

The authors state that only SNP rs1799724 is not in Hardy–Weinberg equilibrium. However, inspection of the genotypes presented in table 2 of the paper reveals that rs2284178 is also not in Hardy–Weinberg equilibrium in the controls (p = 1.3×10⁻⁵). This can occur because of hidden relationship between genotyped individuals or disease association or selection, but most commonly occurs because of genotyping error. …