- As the affiliate center of the University of Minnesota, we have been influenced by their leadership in the field of CFRD. Accordingly, we have made screening for CFRD a priority, which included integrating an endocrinologist into our CF team.
- A review of our established annual patient standard-of-care laboratory results demonstrated 75% of patients in 2010 were completing laboratory testing. Therefore, the timing of the oral glucose tolerance test (OGTT) was changed from an unscheduled basis to becoming part of the outpatient annual lab protocol in an effort to screen the majority of patients.
Target Patient Population
The 2010 CFF guidelines recommend screening patients for CFRD beginning at age 10 years; however, it has been our practice to initiate screening beginning at age 8 years. For the purpose of this project and to increase generalizability for other centers, our results were adapted to include only patients 10 years of age and older.
Definitions
Successful outpatient screening was defined as completion of a 2-hour OGTT obtained by the following process: 1) The patient fasted for 8 hours, 2) a venous blood sample was drawn for a fasting serum glucose, 3) the patient consumed an oral glucose dose of 75 g within 5 minutes of the fasting blood draw, 4) a venous blood sample was drawn 2 hours after glucose administration for the postprandial serum glucose [9]. Patients weighing less than 43 kg received 1.75 g/kg of oral glucose. Outpatients eligible for screening were 10 years of age or older at their first quarterly visit of the year when annual laboratory tests including serum glucose are drawn.
Inpatient screening parameters were determined with guidance from the clinical care guidelines for cystic fibrosis-related diabetes [7], which recommends “monitoring fasting and 2-hour postprandial plasma glucose levels for the first 48 hours.” As this recommendation leaves room for interpretation as far as the quantity and interval of testing, we elected to define a successful screening as completion of one 2-hour postprandial plasma glucose level within 24 hours of admission plus one fasting glucose level within 48 hours of admission. If a patient was identified as having a fasting level ≥ 125 mg/dL or a 2-hour postprandial ≥ 200 mg/dL, additional glucose testing continued beyond 48 hours. However, for the purpose of identifying a successful screening, only the criteria of completing one 2-hour postprandial glucose plus one fasting glucose was considered. Successful screening for inpatients who received a course of steroids was defined as completion of three 2-hour postprandial plasma glucose levels within 24, 48, and 72 hours of admission or initiation of steroids. Inpatients eligible for screening were ten years of age or older at the time of admission.
Patients were not included if they were lost to follow-up for longer than 1 year or were seen for 2 or more quarterly visits at another CF center. Additionally, patients were not eligible if they had been previously diagnosed with CFRD.
Ethical Considerations
Ethical approval for this project was provided by Children’s Hospitals and Clinics of Minnesota Institutional Review Board.