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

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

1. 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.
2. 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.

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)