Comparison of Meal-Time Dosing of Insulin in Cystic Fibrosis Related Diabetes

Phase 4

Active, not recruiting

Conditions: Cystic Fibrosis-related Diabetes

Interventions: Drug: Insulin
Device: Continuous glucose monitor (CGM)

Registration Number: NCT04533646

Lead Sponsor: Jagdeesh Ullal

Brief Summary: The aim of this study is to assess the utility of CGMs to determine the optimal method to dose meal-time insulin. The investigators will examine glucose excursions in patients with CF who will dose meal-time rapid-acting insulin by carbohydrate counting versus fixed-dose rapid-acting insulin. The carbohydrate ratio and fixed doses will be determined by existing doses, total daily insulin doses, body weight, and insulin sensitivity along with predisposition to hypoglycemia. Bolus insulin dosing is an important part of CFRD management due to the high nutritional demands of these patients. If dosed incorrectly, this could lead to marked hyperglycemia and could worsen nutritional status due to urinary glucose losses. In this project, the investigators will perform a within-subjects' comparison of the 2 standard methods of meal-time rapid-acting insulin dosing.

Detailed Description: Background and Introduction Cystic fibrosis-related diabetes (CFRD) is the most common extra-pulmonary comorbidity in patients with cystic fibrosis (CF). CFRD is also associated with an accelerated decline in pulmonary function, increased pulmonary exacerbations, and increased mortality. Continuous glucose monitoring (CGM) involves the use of a small disposable sensor sited in the subcutaneous interstitial fluid that makes frequent glucose measurements. There is data suggesting that the Medtronic iPro continuous glucose monitors (CGM) can predict hemoglobin a1c levels in patients with CFRD.

The aim of this study is to assess the utility of CGMs to determine the optimal method to dose meal-time insulin. The investigators will examine glucose excursions in patients with CF who will dose meal-time rapid-acting insulin by carbohydrate counting versus fixed-dose rapid-acting insulin. The carbohydrate ratio and fixed doses will be determined by existing doses, total daily insulin doses, body weight, and insulin sensitivity along with predisposition to hypoglycemia. Bolus insulin dosing is an important part of CFRD management due to the high nutritional demands of these patients. If dosed incorrectly, this could lead to marked hyperglycemia and could worsen nutritional status due to urinary glucose losses. In this project, the investigators will perform a within-subjects' comparison of the 2 standard methods of meal-time rapid-acting insulin dosing.

Hypothesis:

1. Postprandial interstitial fluid glucose levels in participants who utilize carbohydrate counting to dose mealtime rapid-acting insulin will have improved control as defined as the area under the curve and time in target compared to participants who used fixed-dose mealtime insulin

2. Participants who utilize carbohydrate counting will have fewer hypoglycemia events compared to participants who use fixed-dose meal-time insulin

Specific Aims:

1. To compare within-subject glucose excursions defined as the percentage of time in target glucose level, percentage of glucose in target, and peak postprandial glucose with fixed insulin dosing versus carbohydrate count based insulin dosing.

2. To compare the frequency and duration of hypoglycemia (defined as the daily, weekly, and average duration of the event) between insulin delivery methods described above.

3. To test the use of 'rule of 500' for carb counting estimation in patients with CFRD

4. To compare the effect of two methods of rapid-acting insulin delivery on fasting glycemia

Recruitment & Eligibility

Status: ACTIVE_NOT_RECRUITING

Sex: All

Target Recruitment: 13

Inclusion Criteria

Age >18 age of years
Diagnosis of cystic fibrosis related diabetes
Using basal bolus insulin
Cystic Fibrosis with Lung Transplantation

Exclusion Criteria

Use of continuous glucose monitors
Patient unable to check fingerstick blood sugars

Study & Design

Study Type: INTERVENTIONAL

Study Design: SINGLE_GROUP

Arm && Interventions

Group	Intervention	Description
Fixed Dosing, Followed by Carbohydrate Counting	Continuous glucose monitor (CGM)	Dosing of premeal insulin with fixed doses
Fixed Dosing, Followed by Carbohydrate Counting	Insulin	Dosing of premeal insulin with fixed doses

Primary Outcome Measures