This study found that 10.5% of those with type 1 diabetes were using CSII in Ireland in 2016. Overall, the uptake of CSII in children and adolescents was five-fold higher than in adults. The uptake was the highest, at 38%, in the youngest age-group (0–14 years) and was significantly lower with increasing age. There was significant geographical heterogeneity in CSII uptake with a four-fold variation in uptake across regions for children and adolescents, and five-fold for adults.
In comparison to other countries where CSII therapy is fully reimbursed (all Western European countries), the uptake in Ireland is relatively low. The average uptake in Nordic, Central and Western countries was 15–20% in 2010 . The uptake in Ireland is even lower than in other developed countries with no public funding, where CSII is available mainly to those with private health insurance. In 2014, 12% of the population in Australia , and 59% of those with type 1 diabetes participating in the T1D Exchange clinic registry in the United States  were using CSII. However, the T1D Exchange registry includes 16,061 participants from 76 diabetes US clinics (38 adult and 38 paediatrics), so this figure may not represent that national picture as a whole.
The uptake of CSII in children and adolescents in Ireland (34.7%) is similar to that in the UK where it was reported as 35.7% in those aged < 18 years in England and Wales in 2019  and in the 2017 Scottish National Survey . However, the uptake of CSII in these countries is generally lower than in other Western countries. The highest uptake of CSII in children and adolescents was observed in Slovenia (74%), with Sweden and Denmark also having > 50% uptake) . The SWEET Registry (> 30 paediatric clinics) suggests an average of 44% uptake across Europe (2016) , and 60% of children and adolescents included in the US T1D Exchange clinic registry (38 clinics, 8,483 participants aged < 18 years),  were using CSII in 2014.
In adults, the uptake of CSII in Ireland is also lower than in other countries where this mode of treatment is reimbursed . Uptake has been reported to vary from 9.4% in Scotland , to 15% in England  and Italy  (data from 2017), 21% in Denmark (in one region) , 22% in Sweden (data from 2015) , 24% in Germany, Austria, Switzerland and Luxemburg (data from 2017) . More recent data suggest that uptake of CSII in German adults has risen to 37% in 2017 . Data from the United States (US) suggests that the uptake of CSII was even higher (59%) in adults in 2014 , but for reasons outlined above, unlike the German data, the US figure may not be representative of the population as a whole [14, 23]. Uptake of CSII in Irish adults is similar to Wales (6.7%) , and to findings of the national audit of CSII care in the UK conducted in 2012 . The authors of the UK report concluded that this prevalence was “well below the expectations of the National Institute for Health and Clinical Excellence (NICE) guidelines (15–20%) or the European average (15%)” and, therefore, steps have been undertaken in the UK, in particular in England, to improve the uptake [15, 26, 29]. As a result, uptake in adults in England and Scotland has doubled since 2012 [15, 26], but this is still below that in the Nordic countries, Germany or the United States [10, 23, 27, 28]. In Ireland, there are no standardized criteria or clinical recommendations for the use of CSII therapy in adults at present , which may be one of the factors for the low uptake of CSII. Commencement of CSII is usually at the discretion of the physician and team looking after the patient although aiming to optimize control, limit hypoglycaemia, improve hypoglycaemia awareness and personal preferences would be common indications. Having more firm guidelines could direct physicians to recommend CSII more often. On the other hand, bearing in mind lower uptake in the UK when comparing to Nordic countries, strict criteria, as those in the NICE guidelines, may have an impact on the poor uptake of CSII also. It is worth to note, that many health-care professionals in Ireland receive their postgraduate training (as well as training to provide CSII services) in the UK, therefore the NICE criteria are well-known by significant percentage of specialists in diabetes in Ireland. Other possible barriers to uptake, in particular in adults, might be similar to those explored by Italian researchers. According to the Third Italian Survey of CSII, high costs of CSII and lack of multidisciplinary teams are perceived as limiting factors for CSII uptake . Another barrier might be related to people with diabetes lack of willingness to be attached to a device and a burden associated with technology use [32, 33].
The diversity in uptake of CSII between different age groups is common. Authors of the study conducted in Sweden concluded that people aged between 20–30 years were more than twice as likely to initiate use of CSII than those aged 40–50 years , and data from registries suggest that younger people with type 1 diabetes use CSII more often than older adults [15, 26]. CSII is recommended by ISPAD as a preferred mode of treatment in the youngest population . CSII is often initiated in pre-school children due to their and their families’ needs related to unpredictable food patterns, low insulin requirements, reduction in the number of injections, ease of insulin delivery and needle-phobia , which helps explain why CSII is used more by younger people . These needs have been recognized by the Irish National Paediatric Clinical Programme which introduced a model of care for the provision of CSII in children aged ≤ 5 years in 2012 . This policy document recommends offering CSII to every child with type 1 diabetes under the age of 5 years, which may have contributed to the large difference in uptake between paediatric and adult populations.
Evidence on geographical variation in CSII uptake [15, 24, 26, 36] is lacking. Where evidence is available, for example, in Scotland, the variation was found to be two-fold from 27.1–60% in the paediatric population and 6.7–15.2% in adults . This variation was not as high as that found in our study with a five-fold variation where, in a small number of areas in Ireland, the uptake in adults was very low (2–3%). Similarly, geographical disparity was observed in Italy - even though the Italian health system covers the cost of devices (similar to Ireland); geographical disparity was explained by different regional regulations in terms of prescription rules and requirements . In Ireland, regulations are the same, but this diversity in uptake might be related to the local funding, as different local health offices have different budget .
4.1 Strengths and limitations
The main strength of this study is that it is population-based, nationwide and based on objective data. Our regional findings relate to the residence of those with diabetes and not where they receive their diabetes care; thus the findings accurately describe local access to CSII. This is the first study describing the uptake of CSII in all regions and the entire population of people with type 1 diabetes in Ireland. Data based on prescriptions claimed for CSII sets are a reliable and accurate source of information regarding CSII utilization.
This study has some limitations. It was not possible to monitor discontinuation of CSII, where others have shown discontinuation rates in the range 1–4% . Although the numbers using CSII reported are accurate, the uptake rates may be impacted on by the definition of type 1 diabetes cases, which was based on diabetes-specific prescriptions included in the pharmacy claims database . As information on the diagnosis (i.e. ICD-10 codes) is not available in the HSE-PCRS database and there is no diabetes registry in Ireland, some cases of people with type 2 diabetes receiving basal-bolus therapy or CSII may have been misclassified as type 1 diabetes. In addition, as the HSE-PCRS database is mainly used for the administrative purpose and does not contain any other medical information, there was no possibility to monitor the outcomes of CSII use, i.e. in levels of glycated haemoglobin (HbA1c). Moreover, because continuous blood glucose (CGM) sensors are not included in the HSE-PCRS database (funding is covered from a different budget), we were unable to investigate the uptake of sensor-augmented insulin pump therapy use.
4.2 Conclusions and future research
Uptake of CSII remains low in Ireland when compared to other countries where, like Ireland, CSII is fully reimbursed. The uptake is five-fold higher in children/adolescents than in adults. Our regional findings accurately describe local access to CSII and suggest this access is unequal. This study highlights the potential under-utilisation of CSII in Ireland and suggests that further studies exploring potential barriers, both from the health-care providers’ and patients’ perspectives, are warranted. An understanding of the reasons for the low uptake of CSII will have important implications for improving the quality of care for people living with type 1 diabetes in Ireland. These findings will help to inform health service users and policymakers, and can help to support health-service planners in making decisions on health-service resource distribution. Also, our study suggests that in a country without a national diabetes register, routinely collected administrative pharmacy claims data can be utilized to estimate the uptake of CSII. Finally, this study adds to limited international evidence on the uptake of CSII therapy in those with type 1 diabetes.