Introduction
The relationship between inpatient hyperglycemia and poor clinical outcomes has been demonstrated in several observational studies.1–5 Treatment of hyperglycemia is associated with decreased mortality and morbidity among hospitalized patients.6–8 On the basis of these data, good glycemic control in hospitalized patients has been emphasized by many professional organizations.9 ,10 The current American Diabetes Association (ADA) guidelines recommend insulin as the preferred treatment for hospitalized patients.11 It is recommended that most critically ill patients should receive insulin infusion therapy and non-critically ill patients should receive basal-bolus insulin therapy in the hospital. Non-insulin hypoglycemic agents are not recommended due to multiple contraindications against many of these agents in acutely ill patients. For example, insulin secretagogues can cause hypoglycemia due to poor and unreliable nutritional intake in a hospitalized patient. Metformin and sodium glucose transporter (SGLT)-2 inhibitors are contraindicated in the presence of renal insufficiency or in patients at risk of developing renal insufficiency. Thiazolidinediones take a long time to act and are contraindicated in the presence of congestive heart failure or hepatic dysfunction. Moreover, many non-insulin agents including metformin and GLP-1 agonists can cause gastrointestinal side effects that are undesirable in an already sick hospitalized patient.
None of the above contraindications apply to dipeptidyl peptidase-4 (DPP-4) inhibitors. If effective, DPP-4 inhibitors may be preferable over insulin because of the low risk of hypoglycemia. Hypoglycemia is associated with increased mortality and morbidity among hospitalized patients,12–14 and ADA guidelines strongly recommend avoiding hypoglycemia.11 DPP-4 inhibitors may also reduce glycemic variability that is associated with poor clinical outcomes.15 ,16 Therefore, we conducted a study with the aim of testing the safety and efficacy of DPP-4 inhibitor, saxagliptin, in non-critically ill hospitalized patients with type 2 diabetes mellitus (T2DM).
Study design and methods
This was an open label randomized controlled clinical trial (ClinicalTrials.gov identifier NCT02182895) conducted at a single center. The Partners HealthCare Institutional Review Board approved the study protocol, and all participants provided a written informed consent. Patients older than age 18 years with T2DM and HbA1C ≤7.5% on a ≤1 non-insulin hypoglycemic agent or HbA1C ≤7.0% on ≤2 non-insulin hypoglycemic agents were enrolled into the study after admission to the hospital for a non-critical illness. HbA1c was measured at the time of admission (unless available within the past 3 months) in all patients with diabetes as a standard of care. Exclusion criteria included admission to the intensive care unit (ICU), a history of diabetic ketoacidosis or hyperosmolar state, insulin treatment before admission to hospital, unable to take oral food or medications, systemic steroid use, pregnancy or breastfeeding, a history of pancreatitis or active gallbladder disease, end-stage renal disease on dialysis, hypersensitivity to saxagliptin or another contraindication against saxagliptin, and inability to provide an informed consent.
Eligible participants were randomized by computer-generated numbers to one of the two groups: (1) DPP-4 inhibitor therapy: saxagliptin and (2) standard therapy: basal-bolus insulin regimen. The study statistician generated the randomization scheme using the web site randomization.com and kept it hidden. The investigators were unaware of the treatment assignment until the participant had signed the consent form and was determined to be eligible for the study.
The DPP-4 inhibitor therapy group received saxagliptin 5 mg daily except for patients with eGFR <50 mL/min or using strong CYP3A4/5 inhibitors (eg, atazanavir, clarithromycin, indinavir, itraconazole, nefazodone, nelfinavir, ritonavir, saquinavir, telithromycin) who received saxagliptin 2.5 mg daily. Patients in the standard therapy group received basal-bolus insulin treatment at a starting dose of 0.5 units/kg/day, given half as insulin glargine once daily and half as insulin aspart divided into three equal doses before meals. However, a lower insulin dose was allowed at the discretion of the treating team if oral intake was poor or unpredictable. The goal of therapy was to maintain a fasting blood glucose (BG) concentration between 70 and 140 mg/dL and all other BG values <180 mg/dL. The doses of insulin were adjusted daily by 10–20% to achieve these goals as per the standard practice.
In addition, both groups received the correctional sliding scale insulin therapy with insulin aspart before each meal and bedtime starting with 1 unit at BG >150 mg/dL and increasing by 1 unit for each 50 mg increment. Point of care BG levels were monitored before meals and at bedtime as per current standard practice. As a safety measure, two consecutive BG values >200 mg/dL in the saxagliptin arm led to withdrawal from the study and a switch to the basal-bolus insulin regimen. Patients were also withdrawn from the study if transferred to the ICU, started on systemic glucocorticoids, or became unable to take oral meals.
The primary outcome of this study was the mean daily BG level obtained by point of care testing during study days 2–5. For those discharged before day 5, data were collected until the time of discharge. For those staying longer than 5 days, the study was stopped on day 6 and patients were switched to standard care with basal-bolus insulin therapy. Secondary outcomes included proportion of BG readings in 70–140 mg/dL range, average dose and number of insulin injections, incidence of hypoglycemia (BG <70 mg/dL), incidence of severe hypoglycemia (BG <50 mg/dL), incidence of hyperglycemia (BG >200 mg/dL), treatment failure with DPP-4 inhibitor, and length of hospital stay.
All patients enrolled in the study were asked if they would agree to a continuous glucose monitoring (CGM) insertion. A subset of patients agreed and underwent CGM (iPRO2, Medtronic) to obtain data for glycemic variability. Glucose SD, mean amplitude of glycemic excursions (MAGE) and continuous overlapping net glycemic action (CONGA) were derived from the CGM data using software developed by Hill et al.17 ,18
A well-validated inpatient diabetes treatment satisfaction questionnaire (DTSQ-IP), items 1–16, was administered before the time of discharge.19 This questionnaire had 16 items that were scored on a scale of 0–6. For all the items except for items 2 and 3, ‘0’ indicates lowest satisfaction and ‘6’ indicates highest satisfaction. For items 2 and 3, ‘0’ indicates highest satisfaction and ‘6’ indicates lowest satisfaction.
Statistical analysis
With the mean daily BG as the main outcome, a sample size of 33 randomized to each treatment arm was determined to achieve at least 80% power to test the null hypothesis of saxagliptin inferiority relative to basal-bolus insulin, with 20 mg/dL as the a priori non-inferiority margin, and a within-group SD of 31 mg/dL.20 The number enrolled was 74 because of dropouts and missing data for some. Along with the non-inferiority hypothesis test for the mean daily BG, the upper limit of a one-sided 95% CI around the observed difference between arms was presented. The mean daily BG level during hospital included days 2–5. Day of enrollment into the study was defined as hospital day 1. All continuous data were summarized as mean±SD and categorical data as number with percent. The Wilcoxon-Mann-Whitney test was used to compare continuous variables, and the χ2 test was used to compare categorical variables. Data were analyzed using software SAS V.9.4.