Design of a multi-site multi-state clinical trial of home monitoring of chronic disease in the community in Australia

Table 6 Power calculations for some selected variables

Outcome measure all on the monthly scale	Effective sample size?	Assumed normal distribution	Shift amount (K)	SPower
PBS Total cost	30	Log(PBS Total cost+1)	1	1.00
MBS out of hospital costs	30	Log(MBS out of hospital costs+1)	1	1.00
MBS in hospital costs	30	Log(MBS in hospital costs+1)	1	0.84
Number of hospital admissions	30	Square root the number of hospital admissions	0.5	0.99
Number of GP visits during working hours	30	Square root of number of GP visits during working hours	0.5	0.89
Number of GP visits outside of working hours	30	Square root of number of GP visits outside of working hours	0.1	0.50
Total number of GP visits	30	Square root of total number of GP visits	1	0.97
Total number of either Specialist, Psychiatric, Allied Health visits and Procedures	30	Square root of total number of either Specialist, Psychiatric, Allied Health visits and Procedures	1	0.77
Total number of Laboratory tests	30	Square root of total number of Laboratory tests	1	0.97
Number of Laboratory	30	Square root of number of Laboratory	1	0.96
Tests		Tests

The actual results may be much more complicated than this because the differences between the outcome variables may be auto correlated. This is particularly true if the test patient and the matched control patient outcome measures have different time series trends. Testing of whether the matched differences are auto correlated will be carried out when data becomes available but is not expected to be a significant problem.

ISSN: 1471-2458