Association of sister chromatid exchange frequencies in patients with ankylosing spondylitis with and without HLA-B27.

BACKGROUND The analysis of sister chromatid exchange (SCE) is a cytogenetic technique used to show DNA damage due to an exchange of DNA fragments between sister chromatids. OBJECTIVE To determine whether HLA-B27 positive patients with ankylosing spondylitis (AS) were associated with higher SCE frequencies than patients without B27. METHODS Lymphocytes from 38 patients with AS (15 women, 23 men) and 34 control subjects were examined. Peripheral lymphocytes were cultured in darkness for 72 hours in BrdU added culture. Metaphase chromosomes were stained with a fluorescence and a Giemsa stain after a standard harvest procedure. RESULTS The frequency of SCE was significantly increased in patients with AS compared with controls (p<0.001). Furthermore, the SCE frequencies in patients with positive HLA-B27 was much higher than in patients with negative HLA-B27 (p<0.001). The difference between SCE frequencies in the control groups with and without HLA-B27 was not significant. CONCLUSION There is a strong association between HLA-B27 and the frequencies of SCE in patients with AS.