Of 5,051 physicians contacted, 282 (6%) GPs agreed to the telephone interview and the mailing. A total of 97 (2%) GPs scheduled an interview appointment but subsequently did not complete the interview. The proportion of physicians who were male was about equal between the GPs who received the intervention (66%) and physicians who declined (67%), p = 0.7366. GPs who received the intervention had similar years of experience (mean ± standard deviation, 24 ± 10 years since medical school) as GPs who did not receive the intervention (23 ± 10 years since medical school), p = 0.9697.
displays the proportion of split statin prescriptions written by ChIPS GPs as compared to GPs who did not receive the intervention. At the beginning of the baseline period, 2.6% of all statin prescriptions were split. This proportion rose slowly to roughly 4% in both groups by the end of the 22 month baseline period. Among non-participating GPs, the splitting frequency continued its slow increase at the rate of 0.75% per year, leveling off at 4.4% beginning in month 32. In contrast, during the 13 month ChIPS intervention period, ChIPS GPs’ splitting frequency suddenly changed its rate of increase to 3% per year, leveling off at 7.5% of prescriptions in month 32. Thus the absolute splitting increase was 3.1% among ChIPS GPs. Starting in November 2006 and continuing throughout the 22 month follow-up period, the differences between the two groups persisted, with splitting declining slightly among both groups. ChIPS physicians’ increased splitting rate translates to an additional 5,434 split statin prescriptions during the intervention and follow-up periods.
Proportion of Prescriptions for Statins in BC that were Split Before and After Chart Insert Pilot Study (CHIPs) in British Columbia (October 2003 to July 2008)
Among 187 physicians who wrote five filled statin splitting prescriptions in each of the three observation periods, 26 (14%) increased their proportion of split statin prescriptions by 10% or more (), and 39 (21%) by 5% or more between the baseline and follow-up periods. A total of 12 (6%) GPs decreased their proportion of split prescriptions by 1% or more; the highest decrease was 5.6%. Almost a third of prescribers had relative changes within ± 1%; 6 (3%) had no change at all.
Distribution of Splitting Increases Across 187 Physicians in the Chart Insert Pilot Study (ChIPS), Post-ChIPS Relative to Baseline
In , results of the multivariable analysis among prescriptions to new statin patients and prescriptions to all statin patients are presented. In the new user analysis, after adjusting for baseline differences in splitting frequency between groups, ChIPS GPs increased their splitting frequency by 68% in the 3 years following the intervention compared to all other prescribers. Physicians were less likely to split prescriptions for patients aged 80 or older as compared to patients aged 55 – 59. Splitting was 26% more likely for female patients than for male patients, and 33% more likely for patients with income < $20,000 compared to those with income > $28,000. Physicians were 65% less likely to split a prescription for a patient with full prescription drug coverage than for one with no prescription drug coverage. GPs were more than twice as likely to split statin prescriptions as compared to specialists, and all physicians were 3.4 times as likely to split statins if their last statin prescription had been for splitting. Compared to a prescription for fluvastatin, which cannot be split and so provides a reference group for GPs who choose not to split statins, physicians were 45 times as likely to write a split prescription for lovastatin, and between 7 – 20 times more likely to split all other statins.
Multivariable analysis of statin splitting in the Chart Insert Pilot Study (ChIPS) in British Columbia (October 2003 to July 2008)
The secondary analysis among all statin patients produced largely the same results, although weakened the magnitude of effect. For example, after adjusting for baseline differences in splitting frequency between groups, ChIPS GPs increased their splitting frequency by 32% in the intervention period and by 61% in the follow-up period.