3.1. Outcome measures
A greater benefit from leech therapy than from topical diclofenac was observed in the primary outcome measure, change of total pain of the thumb joint after day 7. The total (±SD) pain score was reduced from 59.6 (±13.8) to 27.1 (±20.6) in 7 days in the leech therapy group and from 50.6 (±13.3) to 46.9 (±18.5) in the diclofenac group (Fig. 2) resulting in a highly significant between group difference -26.5 (95%CI -40.3; -12.7; p = 0.0003, repeated measurement ANCOVA). The group difference persisted at day 30 (-26.5; 95%CI-40.4; -12.7) and increased with day 60 (-34.1, 95%CI: -47.9; -20.2; p < 0.0001). A significant and comparable group difference favoring the leech therapy was evident among all three subscales of pain (Table 2).
In addition, disability in daily life as assessed by the DASH score improved rapidly with leech therapy. This effect was maintained at days 30 and 60 and resulted in significant group differences favoring leech therapy at all time points. Quality of life was reduced at baseline in both groups and improved only in the leech therapy group to a relevant extent resulting in significant between group differences at days 30 and 60 (Table 3). Grip strength increased in the leech group from 42.5 ± 14.1 N to 50.8 ± 14.6 N at day 7 and 57.6 ± 10.2 N at day 60. In the control group grip strength remained unaffected at day 7 (47.5 ± 16.1 N to 47.4 ± 7.0 N) and slightly increased with day 60 (50.7 ± 16.6 N) resulting in a mean group difference of 10.2 (95%CI 1.8 to 18.5; p = 0.021).
The use of rescue medication was comparable in both groups throughout the study. Within the first 7 days two patients in each group had taken any oral rescue medication. On average, recourse to rescue medication was needed on fewer than 3% of all study days without significant differences between the groups.