Information for health care professionals - CFRD
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Information for health care professionals

CF-related diabetes

Cystic fibrosis related diabetes is a common complication of cystic fibrosis. It occurs in around 10-15% of children with CF, and upto 50% of aults with CF by the time they are 30 years old. CFRD is usually associated with pancreatic exocrine dysfunction and the use of oral corticosteroids will increase the tendency to develop diabetes. CFRD is associated with loss of lung function independent of other effects of CFRD (such as weight loss and general ill-health).

Screening for CFRD

Please see our guideline, agreed with our diabetes colleagues here.

The following groups of children should be screened for CFRD:

  • All children over the age of 12 - screening to take place annually
  • All children (of any age) where there is unexplained weight loss or loss of lung function
  • All children (of any age) with symptoms of hyperglycaemia - tiredness, polydypsia, polyuria
  • All children (of any age) with an HbA1c > >42 mmol/mol (6.0%). HbA1c is measured in all children at annual review

Our preferred method of screening is home blood glucose monitoring, either with a glucose monitor and test strips or with a continuous glucose monitor (CGM). If the family are provided with a glucose monitor and test strips, they are asked to carry out pre and post prandial glucose testing over a 3 day period. Post prandial glucose should be measured 2 hours after a meal. In children with apparently normal home glucose monitoring results. Glycaemic control is worse when patients are on steroids or during an infective exacerbation. Results of screening undertaken under these circumstances may not reflect the patient's usual glycaemic control.

CFRD is diagnosed if fasting blood glucose is over 8mmol or if post prandial blood glucose is over 11mmol or if any blood sugars are over 8mmol AND HbA1c is above 6%. When CGM devices are used, they are interpretted according to the table (from the Bromton guidelines):

Diagnostic category CGM values Management
CFRD 2 x peaks >11.1mmol/l and >10% of time >7.8 Start insulin
Impaired glucose tolerance No more than 1 peak >11.1mmol/l and/or >10% of time >7.8mmol/l Consider insulin
Repeat CGM in 6 months
Indeterminate glucose homeostasis 4.5-10% of time >7.8mmol/l or hypoglycaemia Close monitoring Dietary modification for hypoglycaemia/hyperglycaemia
Repeat CGM in 12 months
Normal No peaks >11.1mmol/l and <4.5% of time >7.8mmol/l No intervention required.
Repeat CGM when indicated

We do not use the oral glucose tolerance test, but it is used by some CF centres. In this test 1.75g/kg glucose (maximum 75g) is taken orally. Blood glucose is measured 2 hours later. A level under 7.8mmol/l is normal. 7.8mmol/l to 11mmol/l is impaired glucose tolerance and more than 11.1mmol/l is diabetic.

Treatment for CFRD

CFRD is treated with insulin. The decision to start treatment is a joint consultant decision between the CF team and the diabetes team. Starting insulin should only be done whilst children are in-patients. Before treatment is started the diagnosis and its implications will be explained to the child and family. This will usually be a joint meeting with a CF and diabetes consultant. The diabetes team will chose the type of insulin therapy to be used. In broad terms the following guidelines are used:

  • if there is ONLY post-prandial hyperglycaemia: use novorapid (insulin aspart) before meals
  • if there is fasting hyperglycaemia and post-prandial hyperglycaemia: use basal bolus -lantus (insulin glargine) plus novorapid
  • if there is intermittent hyperglycaemia with no fixed pattern: use levamir (insulin detemir)

The family and child will need to learn how to give the insulin, monitor blood sugar, recognise and deal with hypoglycaemia, and make some modifications to the child's diet.

Follow up

  • For children or teenagers on once or twice daily insulin, and can maintain HbA1c < 7.5%, the CF team will monitor HbA1c (4 monthly), review blood sugar monitoring and check injection sites.
  • Children and teenagers on a basal bolus regime or who are using carbohydrate counting will in addition to their CF clinic appointments need to attend 3 monthly diabetes clinics. In these circumstances the diabetes clinic will monitor the HbA1c.
  • All children and teenagers with CFRD will be seen in diabetes clinic once per year for annual screening of diabetes complications.

Transition

  • Teenagers who have good control of their CFRD (HbA1c<7.5%) on once or twice daily insulin will be seen in the joint Adult CF/Diabetes clinic when transitioned to the Adult teams.
  • Teenagers who have required more intensive input from Diabetes team should be transitioned via the Diabetes Transition Clinic at OCDEM, moving into the young adult clinic for follow up.