Comparing Two Different Approaches in the Screening of Cystic Fibrosis Related Diabetes (CFRD)

A Comparative Analysis of the Clinical Efficacy of Two Approaches in the Screening for Cystic Fibrosis Related Diabetes in Adult With Cystic Fibrosis: i) a Selective Approach; ii) an Unselected Annual Oral Glucose Tolerance Test

The incidence of cystic fibrosis related diabetes (CFRD) has risen significantly as patients' survival improves. Early diagnosis of CFRD is crucial to prevent the unnecessary deterioration of lung function and nutritional status, both of which affect the patient's overall survival. The oral glucose tolerance test (OGGT) is the accepted method for detecting CFRD. The Cystic Fibrosis Trust guidelines (2004) recommend that patients with CF over the age of twelve years should be screened annually. Most hospitals use an annual OGTT. Performing OGTT on all CF patients is inconvenient and may not be cost effective, as patients have to starve overnight and need to spend an extra 2 hours in the hospital in addition to all the other annual review tests. In our centre, a selective approach is used. If patients have an abnormal random blood glucose and /or abnormal glycosylated haemoglobin (HbA1c) and/or symptoms of hyperglycaemia or unexplained weight loss then an OGTT will be performed. The aims of this study are To compare the clinical efficiency in the screening for CFRD in the two different methods: i)a selective approach , ii)an unselected annual OGTT for all patients. To compare the cost effectiveness of the two approaches in the screening for CFRD.

CFRD affects 30% of all patients with cystic fibrosis (CF) by the age of twenty-five. Early diagnosis of CFRD is crucial to prevent the unnecessary deterioration of pulmonary function and nutritional status, both of which affect the patient's overall survival. The selective approach takes less patient time and is less expensive. If it is equally accurate it should be used routinely. The oral glucose tolerance test (OGTT) is the accepted method for detecting CFRD and the Cystic Fibrosis Trust guidelines recommend that patients with CF over the age of twelve years should be screened annually. Yung et al, questioned this approach and argued that performing OGTT on all CF patients is inconvenient and may not be cost effective, as patients have to starve overnight and need to spend an extra 2 hours in the hospital in addition to all the other annual review tests. In this study, a selective approach in performing OGTTs in the screening for CFRD will be used; this includes the use of a combination of clinical and biochemical criteria that of abnormal random blood glucose and /or abnormal glycosylated haemoglobin (HbA1c) and/or symptoms of hyperglycaemia, or weight loss.

Adults, Cystic Fibrosis Related Diabetes, Screening, Oral glucose tolerance test, Royal Brompton & Harefield Foundation Trust

There is only one arm. All patients in the study had the same procedures (ie. an OGTT). Investigators used the screening criteria in parallel to this.

A study subject has an abnormal OGTT will be referred to a cystic fibrosis consultant who is not involved in the study.

To identify if using the selective approach to screen for CFRD is as accurate as screening all patients with OGTT at annual review.

Patients identified for OGTT based on the selective approach by the two independent reviewers will be compared. Patients will form two groups: i)those identified as needing OGTT, ii)those on whom they considered it unnecessary The results of the two groups will then be compared with the data obtain from OGTT to which the two reviewers were 'blinded'

Calculate the cost of glucose powder and laboratory analysis for each OGTT. Compare the cost effectiveness of carrying out OGTT on patients identified by the selective approach with the cost of carrying out OGTT on all patients.

Inclusion Criteria: first one hundred consecutive clinically stable patients with CF attending annual review from January 2009 16 years of age and over will be eligible for the study. Exclusion Criteria: patients with an existing diagnosis of CFRD. patients with an infective exacerbation (i.e. on a new course of antibiotics)