Improving screening in a Paediatric cohort for cystic fibrosis related diabetes: a quality improvement project
To the Editor,
Screening for Cystic fibrosis (CF) related diabetes (CFRD) can be difficult to achieve consistently. There are multiple guidelines recommending oral glucose tolerance tests (OGTT) for screening1,2. Furthermore, in the last decade CF transmembrane receptor modulator therapy has become available, improving the overall health of children and young people with CF, and potentially reducing the need for regular screening.
Perth Children’s Hospital (PCH) is the only tertiary paediatric hospital in Western Australia. All children and adolescents living with CF in Western Australia and some parts of the Northern Territory are managed at PCH. During the study the cohort included 206 patients, aged 0-18 years. 50% were on CFTR modulator therapy. Screening for CFRD was mostly limited to annual glycosylated haemoglobin (HbA1C) and OGTT for patients admitted to hospital for management of pulmonary exacerbations of CF.
Here, we report a quality improvement project using the process of ‘Plan, Do, Study, Act’ (PDSA) cycles. Baseline assessment was performed to define the current care provided at PCH. Prospective cycles were analysed to assess improvement in screening. The aim of this study was to improve screening for CFRD using OGTT to 50% by 2021. A secondary aim was to characterise children at higher risk for a positive OGTT.
CFRD is different from type 1 and 2 diabetes mellitus and has characteristics that can be seen in both type 1 and type 2 diabetes including relative insulin deficiency and insulin resistance3,4. CFRD is more common with increasing age, in females, and pancreatic exocrine insufficiency. The prevalence from the Australian CF registry in 2019 in 12-17-year olds was 16% with impaired glucose tolerance and 22% with CFRD5. CFRD can cause poor growth and increase the risk of pulmonary exacerbations due to hyperglycaemia promoting bacterial growth and increased thickness of secretions4. Of note, a systematic review in 20196 showed no difference in Body Mass Index (BMI), Forced Expiratory Volume in 1 second (FEV1) in patients with CF and impaired glucose tolerance when compared to those with normal glucose tolerance. Investigations to diagnosed diabetes include HbA1c and OGTT. Neither of these tests are perfect. HbA1c reflects the blood glucose levels over the past 2-3 months. The current recommended level is based on type 2 diabetes when diabetic retinopathy becomes prevalent. Also, HbA1c is often normal at the time of diagnosis of CFRD4. For OGTT, the diagnostic cut offs for CFRD are taken from type 2 diabetes and are designed to prevent microvascular complications, not weight loss and loss of lung function.
The current recommendations from the Nutrition Guidelines for CF in Australia and New Zealand, suggest that all children with CF aged 10 years and above have a yearly OGTT or earlier if symptomatic2. Recommendations from Australian Standards of Care for CFRD, state that yearly screening for glucose tolerance should be performed in all patients with CF ≥ 10 years1. This can be done by either a formal OGTT or random blood glucose testing if symptomatic.
At the start of 2019, there were 99 children and adolescents with CF 11 years and above being managed at PCH. 43/99 (43%) were males. 45/99 (45%) were prescribed CFTR modulator therapy. Four patients were ineligible for screening.
To understand the problem in more detail an audit of all patients with CF was performed. The following data were collected: age, sex, genotype, eligibility for modulator therapy and if prescribed modulator, pancreatic function, OGTT, HbA1c, weight and height, forced expiratory volume in 1 second (FEV1), if admitted in 2019, and if prescribed steroids for more than one month. Ethics approval was granted through the low-risk pathway. Results were reviewed weekly and statistical analysis was performed through Microsoft Excel (2022). We identified 13/92 (14%) eligible patients had an OGTT in 2018. The known prevalence of CFRD was 3/206 (1.4%) and impaired glucose tolerance was 2/92 (2%).
The implementation team consisted of a respiratory advanced trainee, head of respiratory and sleep department and clinical lead for CF. A series of PDSA cycles were conducted to improve screening. A range of methods were used including data collection from electronic results systems for baseline practice and post interventions. The implementation team met post each strategy to discuss results and to plan the next phase.
The cycles were as follows:
Over a two-year period four PDSA cycles were used to improve screening for CFRD. See figure 1 for change in screening for CFRD. By the end of 2019, 23/38 (60%) of inpatients were screened, which was 24% of the total population. Cycles 3 and 4 improved screening to 40% and 63%, respectively. As a result of improved screening, 14/95 (15%) patients were found to have glucose intolerance or CFRD. Patients with abnormal OGTTs were pancreatic insufficient (90%), and prescribed modulator therapy (70%). Their average BMI z score was -0.30 (standard deviation 1.3) and an average best FEV1 predicted of 88% (standard deviation 15.6).