Educational intervention to optimise serum immunoglobulin test use in Irish primary care: an interrupted time series with segmented regression analysis

Background Implementation science experts recommend that theory-based strategies, developed in collaboration with healthcare professionals, have greater chance of success. Aim This study evaluated the impact of a theory-based strategy for optimising the use of serum immunoglobulin testing in primary care. Design and setting An interrupted time series with segmented regression analysis in the Cork-Kerry region, Ireland. An intervention was devised comprisinga guideline and educational messages-based-strategy targeting previously identified GP concerns relevant to testing for serum immunoglobulins. Method Interrupted time series with segmented regression analysis was conducted to evaluate the intervention, using routine laboratory data from January 2012 to October 2016. Data were organised into fortnightly segments (96 time points pre-intervention and 26 post-intervention) and analysed using incidence rate ratios with their corresponding 95% confidence intervals. Results In the most parsimonious model, the change in trend before and after the introduction of the intervention was statistically significant. In the 1-year period following the implementation of the strategy, test orders were falling at a rate of 0.42% per fortnight (P< 0.001), with an absolute reduction of 0.59% per fortnight, corresponding to a reduction of 14.5% over the 12-month study period. Conclusion The authors' tailored guideline combined with educational messages reduced serum immunoglobulin test ordering in primary care over a 1-year period. Given the rarity of the conditions for which the test is utilised and the fact that the researchers had only population-level data, further investigation is required to examine the clinical implications of this change in test ordering patterns.