How is it assessed?

• Diagnostic tests
• Screening at birth
• Sweat test
• Genetic testing
• Other hospital investigations
• Investigations to monitor progress of disease that can be used to confirm disabling effects or care needs
• Information collected at annual review about lung function including test result and their meaning:
• Information collected at annual review about gut function and nutritional status:
• Other complications
• Indicators for severe functional restriction

It is helpful to consider investigations in two ways, those that confirm the diagnosis is cystic fibrosis and those that give information about how the disease is affecting the child.

Diagnostic tests

Screening at birth

All newborns are screened for cystic fibrosis using a heel prick blood test when they are a few days old. This is sometimes called the Guthrie test. The levels of a protein called immmunoreactive trypsinogen (IRT) are abnormally high in babies with cystic fibrosis. The blood is then tested for the commonest CF gene mutations. If 1 or 2 gene mutations are identified and/or if the IRT is high on 2 occasions the diagnosis of CF is suspected (positive screening test). Babies with a positive test will go on to have the sweat test or repeat genetic testing to confirm the diagnosis.

Sweat test

This test measures the amount of salt in sweat on the skin and is a definitive test for cystic fibrosis.

Genetic testing

There are more than 1000 different gene defects known to occur in cystic fibrosis. Genetic testing only tests for the commonest of these so, used as a test by itself genetic testing is not a foolproof method of diagnosing cystic fibrosis. It is most commonly used to enable a family to identify the cystic fibrosis genes in their family and to plan future pregnancies.

Other hospital investigations that may be performed at diagnosis include:

• Bronchoscopy – with biopsy and bronchoalveolar lavage (fluid is squirted in to small areas of the lung and recollected for analysis) - to document appearance of airways, assess level of inflammation and detect occult infection (by analysing the lavage fluid). Only used in some centres.
• Overnight pH probe – a probe is placed in the throat and stomach overnight to assess for gastro-oesophageal reflux. Persistently refluxing stomach contents can be inhaled and adversely affect the lungs. Only used in some centres.
• Other tests may be carried out such as, stool elastase respiratory samples, chest X-ray.

Investigations to monitor progress of disease that can be used to confirm disabling effects or care needs

Children with cystic fibrosis will receive routine monitoring every 1-2 months at a CF clinic as well as having an annual review. They will be seen at least annually by the Regional CF centre team, either at their own clinic or in the CF centre. They may also need urgent review in between routine visits. This section describes the data that is typically collected at the annual review and how it can be used to confirm needs in DLA assessment. The most important information will be that relating to lung function because lung function closely correlates with disability and survival in cystic fibrosis.

Information collected at annual review about lung function including test result and their meaning:

• Record of chest symptoms – e.g. cough, sputum, exercise tolerance, number of exacerbations in the year.
• Usual microbiology - organisms found growing in sputum through the year, chronic colonisation with some organisms indicates greater probability of disability or care needs because the organism accelerates lung damage, the main organism is Pseudomonas aeruginosa. Colonisation with Mycobacterium abscessus is associated with a bad prognosis and significantly increases the burden of care.
• Lung function tests – also called spirometry measures FVC (forced vital capacity – maximum volume of air that can be exhaled in a breath), FEV1 (forced expiratory volume in 1 second) amount of air breathed out during first second of forceful breathing out and a number of other values. FEV1 is the most important. The expected or normal FEV1 for a person can be calculated using their age height and sex and the result expressed as a percentage, for example normal lungs will equal or exceed expected performance and the FEV1 will be 80- 100% or more. In children with cystic fibrosis FEV1 can be reduced. Children less than 6-7 years of age may not produce consistent interpretable results. FEV1 values are recorded at every clinic review, when seen in between appointments, before during and after starting new treatments e.g. before and after intra-venous antibiotics. Results correlate closely with respiratory disability affecting walking as below:

Table - FEV1 measurement and likely disability affecting walking

• Pulse oximetry/Oxygen saturation (SpO2) – tested using an oxygen probe on the finger, normal reading 97 to100%. Home oxygen may be used if readings are repeatedly below 90%. Less than 85% is considered severe. Abnormal overnight oxygen saturation monitoring will indicate worsening respiratory function. Other symptoms of respiratory failure include waking with a headache /increased tiredness.
• Plethysmography – the child is placed inside a small chamber the size a telephone booth and breaths in. Changes in pressure inside the sealed booth are measured and from this the Functional Residual Capacity (FRC) and total lung capacity (TC) of the lungs can be measured. These results cannot be used to determine the presence of respiratory disability and is rarely used.
• Chest X-ray score results may be used to monitor the changes in X-ray appearances seen over time in cystic fibrosis. This information is provided to aid understanding of the medical evidence that may be supplied, X-ray score results should not be used to assess disability in DLA even though abnormal looking X-rays are associated with disability.
• Northern Score – appearance of chest X-rays is scored between 0 (normal looking) and 4(very severe changes associated with cystic fibrosis). Severity of X-ray changes correlate with FEV1.
• Brasfield Score – appearance of chest X-ray is scored between 25 (normal looking) and 5 (very severe changes associated with cystic fibrosis), this score of between 5 and 25 can be used to complete the X-ray findings column in the Chrispin-Norman score – appearance of chest X-ray is scored between 3 (normal looking) and 22 (very severe changes of CF). It requires a lateral chest X-ray to be performed.
• CT scan of the chest – although not performed at annual review routinely, if done may give information on the degree of lung damage.
• Physiotherapy review – techniques used by the child at home are reviewed for effectiveness. Training or modification of home regimen may be advised at the clinic. May be some information from the physiotherapist on the amount of exercise the child is doing and their exercise tolerance. Information on effectiveness of inhaled medication may be in this section.

Information collected at annual review about gut function and nutritional status:

• Dietary assessment by dietician – likely to include assessment of nutritional needs and advice on supplements required or artificial feeding if required.
• Height, weight and growth velocity
• Body Mass Index (BMI)
• Growth charts are used to assess whether nutrition is adequate and whether nutritional support is required

Other complications

• A range of blood tests will be checked at the annual review.
• Oral glucose tolerance tests may be carried out for older children to identify the early stages of cystic fibrosis related diabetes (CFRD)
• continuous glucose monitoring gives more accurate picture of blood sugar variations during normal activities
• Bone scan (DEXA) – to identify osteoporosis (thinning of bones) this may develop because of malnutrition and or use of steroids

The main investigations will be those monitoring lung function. Progression of disease may be scored using various scoring systems, for example to monitor chest X-ray changes. It is expected that all children will have a minimum dataset collected by their Regional CF centre including scoring information. This information can be used to confirm disability where care needs are claimed.

Indicators for severe functional restriction

Any one of the following:

• On lung or liver transplant list
• Terminally ill
• On home oxygen or non-invasive ventilation at night or day and night
• FEV1 <40% of expected
• On artificial feeding regimen, e.g. feeding gastrostomy tube
• Requirement for frequent intravenous antibiotics –more than every 3 months