This study was an adjunct to a randomised controlled trial in a 55 member general practice cooperative serving 97
000 patients in Wiltshire. The design has been described.1
The night nurse telephone consultation service ran over two two-week periods (15-28 October 1997 and 12-25 November 1997) from 11.15 pm until 8 am. Outcome measures were as used in the main trial with one addition: the number of patients attending daytime surgery within three days of a call.1
One of us (FT) visited each surgery to extract details of attendances from patient records.
In the main study 49.8% of calls were handled by the nurse alone. Specifying α=0.1 (0.05 in a one sided calculation) and β=0.2, we calculated that the night nurse service would need to receive 78 calls to establish equivalence with this figure, with equivalence limits being 40% and 60%.3
A one sided calculation was used as we were interested to establish only whether the night nurse intervention produced worse results (lower numbers of calls handled without referral to a doctor) than the evening and weekend service. For other within-trial outcomes, results are presented as relative risks with 95% confidence intervals, calculated with EpiInfo. This trial was not powered to show within-trial equivalence in numbers of adverse events.
During the study 210 callers made 223 calls, 123 in the control group and 100 in the nurse telephone consultation (intervention) group. Follow up was 94% complete: 12 sets of patient records (6%) could not be found, seven in the control group and five in the intervention group. The median age (range) of patients was 34.0 ( 0.01-97.2) years in the control group and 32.5 (0.49-97.0) years in the intervention group. Fifty three patients (43%) in the control group and 44 (44%) in the intervention group were male.
The table shows details of call management and outcome. Altogether 59% of calls (95% confidence interval 48.7% to 68.7%) were handled by the nurse alone. As we were interested only in whether the nurse service handled fewer calls at night, this can be interpreted as showing equivalence with the proportion observed in the main trial. The proportions of calls in which callers received advice from a general practitioner and calls ending in a home visit showed clear reductions, with 95% confidence intervals not embracing 1. A lower proportion of calls resulted in a daytime surgery attendance in the intervention arm, although the 95% confidence interval embraced 1. Other differences had wide confidence intervals.