Use of rational subgrouping to understand variation and opportunity for improvement in time to ultrasound

Objective To understand factors that contribute to variation in time to abdominal and/or pelvic ultrasound in pediatric patients in an emergency department (ED) by utilizing rational subgrouping to assess opportunity for improvement. Methods All abdominal and pelvic ultrasounds conducted in the Alberta Children’s Hospital ED from May 2019 to April 2021 were included. Time of study order and time of study completion were obtained from the electronic health record. Statistical process control (SPC) I-charts were used to analyze the quarterly median number of minutes from ultrasound order to completion. Rational subgrouping was used to stratify the data based on sex, age, and ED shift type, and identify special cause variation between groups. Findings were used to inform local decision-making. Results Special cause variation was detected among subgroups for sex, age group, and shift type. The median time from order of an abdominal and/or pelvic ultrasound to completion of study was 155 min. Females had a median order to completion time of 178 min, while males had a completion time of 131 min. From age 0 to 3, the median time was 110 min, compared to 149 min for ages 4 to 11 and 171 min for ages 12 and older. Day shifts had a median order to completion time of 145 min, compared to 129 min for evening shifts and 269 min for night shifts. Conclusions Longer time to study completion was observed in female patients, older patients, and during night shifts. Use of rational subgrouping supported understanding of variation among subgroups of patients evaluated with abdominal and/or pelvic ultrasound. This allowed informed decision-making regarding opportunities for improvement. Rational subgrouping is a useful methodology in planning QI initiatives as it identifies sources of variation within a nonhomogeneous population and allows for judicious decision-making in a context of limited resources.