Skip to main content

Table 2 Sample size calculations for the three primary outcome measures assuming an 11% reduction in error rates for the simple feedback group and a 50% reduction in error rates for the intervention group

From: Protocol for the PINCER trial: a cluster randomised trial comparing the effectiveness of a pharmacist-led IT-based intervention with simple feedback in reducing rates of clinically important errors in medicines management in general practices

Outcome measure

Patients with a history of peptic ulcer who have been prescribed a non-selective NSAID

Patients with asthma who have been prescribed a beta-blocker

Patients aged 75 years and older prescribed an ACE inhibitor or a loop diuretic long-term without a check of their renal function and electrolytes in the previous 15 months

Median error rate1

(Interquartile range)

5.76%

(3.76% – 7.85%)

1.90%

(1.27% – 3.08%)

19.80%

(15.13% – 32.69%)

Error rate in control group (assuming 11% reduction)

5.13%

1.69%

17.62%

Error rate in intervention group (assuming 50% reduction)

2.88%

0.95%

9.90%

Intraclass Correlation Coefficient (ICC)1

0.01082

0.00657

0.00952

Cluster size1

63

439

105

Inflation factor

1.7

3.9

2.0

Total number of practices required

64

66

12

  1. 1 Estimated using data obtained from 43 general practices contributing to the QResearch database http://www.qresearch.org