The effect of three years of TNF-α blocking therapy on BMD in patients with AS. (A) lumbar spine BMD. (B) hip BMD. Z-scores were calculated to correct for age and gender. Data were available for 92.4%, 93.1%, 89.6% and 64.6% of the 72 patients at 0, 12, 24 and 36 months, respectively. Box-and-whisker plots (Tukey): boxes indicate medians with interquartile ranges; + indicate means; whiskers indicate 1.5 times the interquartile distances; • indicate outliers. a: P < 0.001 compared to values recorded at baseline. b: P < 0.05 compared to values recorded at 12 months. c: P < 0.001 and P < 0.01 compared to values recorded at 12 and 24 months, respectively.