Cystic fibrosis clinical outcomes

Clinical outcomes are broadly agreed, measurable changes in health or quality of life that result from our care. Constant review of our clinical outcomes establishes standards against which to continuously improve all aspects of our practice.

About the Cystic Fibrosis Service

Cystic fibrosis (CF) is a life-limiting disorder that affects more than 10,000 people in the UK. A little under half of those with the condition are children. CF is caused by a defective gene that causes the body to produce abnormally thick and sticky mucus. It is a multisystem disorder, involving many internal organs but primarily affecting the lungs and digestive system.

The Cystic Fibrosis Unit at Great Ormond Street Hospital (GOSH) is a designated specialist centre, which cares for approximately 180 children from newborn to 16 years of age. Most referrals come from the National Cystic Fibrosis Newborn Screening Programme.

We have a full specialist multidisciplinary team of doctors, nurses, physiotherapists, dietitians, pharmacists, psychologists, social workers and administrative staff. The unit works closely with a number of other departments within GOSH, in particular paediatric radiology, endocrinology and gastroenterology. In a small proportion of cases, the care of children is shared between a local ‘network’ hospital and the specialist service at GOSH. Where this arrangement takes place, the outreach team provides a link between the centre and local team. The unit also works closely with North East London Foundation Trust community nursing team to provide a specialist outreach service to children with CF in the Basildon area.

There is a strong research collaboration between GOSH and the other London cystic fibrosis specialist paediatric units. The department has an international reputation for research, particularly in respiratory physiology and measuring lung function in babies.

Clinical outcome measures

1. Lung function

2. Nutritional status

3. Pseudomonas aeruginosa infection rate

How to interpret the graphs

There is natural variation between centres because of differences between the patients receiving care. Using only the national average as a standard makes it difficult to tell if a centres’ outcome are within ‘expected’ variation. For this reason, the funnel plots also show ‘control limits’: the dashed curved lines on the graphs that give them the ‘funnel’ shape. Each graph shows the national average result for all paediatric CF centres in the UK as a horizontal red line in the middle of the funnel.  

If the result for a CF centre is between the two control limits its results are expected. If a result is below the bottom control it is lower than expected, if it is above the upper control limit it is higher than expected.

GOSH's clinic ID is 90. The full list of clinics and their IDs can be found on page 52 of the UK Cystic Fibrosis Registry Annual Data Report 2016 on the Cystic Fibrosis Trust website.

1. Lung function, measured by: Forced Expiratory Volume in 1 second (FEV1)

One of the key measures undertaken to monitor CF lung function is the Forced Expiratory Volume in 1 second (FEV1 ). This measures the proportion of expired air blown out in the first second during a hard and fast breath out. This measure is then compared to that of an average child of the same age, sex, height and ethnicity, who does not have CF. This comparison is against ‘population norms’ to provide a benchmark for a normal range.

In theory, an FEV1 of 100 per cent predicted means that lung function is totally normal. However, we are all slightly different, and lung size is associated with body size, chest size, sex and age. This means that lung function varies between individuals and so somewhat more or less than 100 is still considered to be within normal range.

Fig 2.1b Age adjusted best FEV1 % predicted (GLI) among patients aged 6 amd over, by paediatric centre
Published with the permission of the UK Cystic Fibrosis Registry

In 2016 the national average FEV1 per cent predicted for all those with CF aged 6 and over was 91 per cent. The result for our clinic at GOSH in 2016 was 91 per cent, the same as the national average value and within the control limits. We continue, with our quality improvement programme and other projects (such as the INSPIRE study) striving to increase this value further. It is our goal to transfer our young people to adult services with normal lung function.

2. Nutritional status, measured by: Body Mass Index (BMI)

Body mass index (BMI) is a reflection of nutritional status. BMI is important in CF because research indicates that a good BMI is associated with better outcomes for lung function and survival.

BMI is a number calculated from weight and height and is commonly used as an indirect measure of body fat. In children, we look at BMI in a slightly different way to adults by reporting it as a percentile (indicating the relative position of a patient’s BMI within the range of children of the same sex and age who do not have CF). This is because body fat changes with age and differs between boys and girls.

Fig 2.2 Age adjusted BMI percentile among patients aged 2-15 years by paediatric centre
Published with the permission of the UK Cystic Fibrosis Registry

In 2016, the national average BMI percentile for all those with CF aged 2 to15 was 53. The BMI percentile for our clinic at GOSH in 2016 was 45.1.

Although national guidelines state that the majority of children with CF should have a BMI percentile of 50 or greater, a high BMI does not mean a healthy nutritional state. We need to ensure that the children under our care are fit and healthy and are looking closely at the data and at other measures in a quality improvement initiative so that we can ensure we are doing all we can to achieve optimal nutritional status.

3. Pseudomonas aeruginosa infection rate

The lungs and airways are one of the primary systems affected by CF, so it is essential that we do as much as we can to prevent and actively treat chest infections in order to avoid lung damage. Pseudomonas aeruginosa is a bacterium that can cause significant problems in people with CF. Early aggressive treatment and careful attention to prevention of cross-infection aims to reduce the number of children with chronic Pseudomonas aeruginosa infection.

Fig 2.3 Proportion of patients with chronic Pseudomonas aeruginosa by paediatric centre
Published with the permission of the UK Cystic Fibrosis Registry

In 2016 the national average percentage of patients with chronic Pseudomonas aeruginosa infection in paediatric centres in the UK was 7.5 per cent. The proportion of GOSH patients with chronic Pseudomonas aeruginosa was 5 per cent, below the national average and within the control limits..

Although we continue to be reassured by this data, we certainly cannot be complacent and close attention to cross infection remains high on our list of priorities. Our annual clinic surveillance programme for pseudomonas cross infection continues, where we take samples from as many children as possible in a two month period and any which grow pseudomonas are sent to a specialist laboratory for ‘typing’ to alert us to any cross infection potential or particularly virulent strains. To date there has been no evidence of either within the GOSH clinic.

This information was published in January 2018.