Diabetes Care 30:1044-1048, 2007 DOI: 10.2337/dc06-1328 © 2007 by the American Diabetes Association
Using Continuous Glucose Monitoring to Measure the Frequency of Low Glucose Values When Using Biphasic Insulin Aspart 30 Compared With Biphasic Human Insulin 30A double-blind crossover study in individuals with type 2 diabetes
1 Leicester Royal Infirmary NHS Trust, Leicester, U.K. Address correspondence and reprint requests to Prof. Simon Heller, Professor of Clinical Diabetes, Academic Unit of Diabetes, Endocrinology and Metabolism, Room OU141, School of Medicine and Biomedical Sciences, Beech Hill Road, Sheffield S10 2RX, U.K. E-mail: s.heller{at}sheffield.ac.uk
OBJECTIVERapid-acting insulin analogs in basal-bolus regimens can reduce nocturnal hypoglycemia, so it is conceivable that twice-daily biphasic insulin analogs might reduce hypoglycemia in patients with insulin-treated type 2 diabetes. We used a continuous glucose monitoring system (CGMS) and self-reported episodes to investigate differences in the frequency of low glucose values in patients with type 2 diabetes, using either biphasic insulin aspart 30 (BIAsp 30) or biphasic human insulin 30 (BHI 30). RESEARCH DESIGN AND METHODSThis was a double-blind, two-period, crossover trial involving 160 subjects. After 8 weeks run-in, subjects were randomized to the first of two 16-week treatment periods. RESULTSNo differences in overall incidence of low interstitial glucose (IG) were found. Twenty-fourhour plots of CGMS showed low IG was more frequent at night than during the day and was unrecognized by patients. At night, subjects spent significantly less time (percentage of total CGMS recorded) with IG <3.5 and <2.5 mmol/l during BIAsp 30 than during BHI 30 treatment, respectively (<3.5 mmol/l: 6.36 vs. 7.93% [mean], 0.67 vs. 2.43% [median], P = 0.018; <2.5 mmol/l: 2.35 vs. 2.86% [mean], 0 vs. 0% [median], P = 0.0467). No treatment difference in A1C was observed. CONCLUSIONSOverall rates of low glucose over 24 h were not different but were twice as frequent at night than during the day in individuals with type 2 diabetes. Compared with BHI 30, BIAsp 30 was associated with similar low IG readings over 24 h but with fewer nocturnal episodes and less self-reported nocturnal hypoglycemia.
Abbreviations: BIAsp 30, biphasic insulin aspart 30 BHI 30, biphasic human insulin 30 CGMS, continuous glucose monitoring system IG, interstitial glucose ITT, intent to treat
Insulin is being used earlier in the management of type 2 diabetes to achieve tighter glucose targets, but weight gain and, in particular, hypoglycemia remain important barriers to the success of treatment (1). The progression from oral agents to combination therapy involving insulin, or insulin monotherapy, increasingly includes the use of insulin analogs. This is particularly true for premixed biphasic insulin combinations, although the evidence for benefit compared with conventional premixed insulin is relatively limited. In basal-bolus regimens, the inclusion of rapid-acting insulin analogs is associated with reduced nocturnal hypoglycemia relative to soluble human insulin (2). It is possible that similar effects may also be observed with biphasic insulin preparations. We set out to test this hypothesis in a clinical trial (the REACH StudyRandomized Evaluation of Premix Insulin BIAsp 30 [biphasic insulin aspart 30] in Controlling Hypoglycemia in type 2 diabetic patients) comparing the newer, more physiological, premix analog BIAsp 30 (30% aspart, 70% protaminated aspart) with the conventional human premix biphasic human insulin 30 (BHI 30) (30% regular insulin, 70% NPH insulin), using a continuous glucose monitoring system (CGMS) and self-reported episodes to record the incidence of hypoglycemia.
A total of 160 male and female patients with type 2 diabetes (BMI <40 kg/m2, A1C <9.5%) pretreated with insulin for at least 6 months were recruited to this randomized, double-blind, two-period, crossover trial from 18 centers in the U.K. All oral antidiabetes drugs were stopped at study entry. Patients with a history of severe hypoglycemia or hypoglycemia unawareness were not specifically excluded. Baseline characteristics are shown in Table 1. The trial was performed in accordance with the Declaration of Helsinki and good clinical practice. Patients gave written informed consent before any trial-related activities began.
Treatment regimens During an 8-week run-in, existing insulin therapy was optimized to achieve preprandial blood glucose levels of 57 mmol/l. Patients with A1C 6.58.5% were then randomized to receive BIAsp 30 (n = 70), 100 units/ml, or BHI 30 (n = 75), 100 units/ml, contained in 3-ml Penfill administered dose using NovoPen 3. Randomization was carried out by allocating the next available randomization number to each patient and allocating treatment sequence using a computer-generated code with a block size of four. Randomization was undertaken centrally with the randomization number containing information about the treatment for each patient sealed throughout the trial. To maintain the double-blinded trial design, both types of insulin were injected immediately before breakfast and evening meals (it was deemed unsafe to allow any injection-meal interval for BIAsp 30 due to the rapid action of insulin aspart). After the first 16-week treatment period, patients switched to the alternative insulin for a further 16 weeks, with no washout period. Throughout the trial, participants were free to adjust the dose (in discussion with research staff) according to individual needs once per week. No specific instructions were given with regard to evening exercise or snacks.
CGMS The monitor recorded IG levels every 10 s then stored a smoothed average over 5 min. The range of IG detection was 2.222 mmol/l. The primary end point was the frequency of readings <3.5 mmol/l (IG3.5). IG readings <2.5 mmol/l (IG2.5) were also compared since studies suggest that glucose <2.8 mmol/l is likely to reflect clinically relevant hypoglycemia (3,4). The 24-h data were categorized into total, daytime (06000000 h), and nighttime (00000600 h). Low IG readings were also grouped into episodes, defined as a set of continuous IG readings <3.5 mmol/l (or <2.5), allowing up to two consecutive readings above the threshold within the same episode. If a following episode started within 1 h of the start of the previous episode, they were combined and recorded as one episode.
Self-monitoring of blood glucose and self-reported episodes of hypoglycemia
Adverse events
A1C
Diabetes treatment satisfaction
Statistical analyses Self-reported hypoglycemia was tested using Wilcoxon's signed-rank test; the timing of low IG episodes was tested using the Kruskal-Wallis test, and proportions were tested using Fisher's exact test. Missing A1C values at visit 2 were replaced by the visit 1 value for the same patient, using the last-observation-carried-forward method. No other missing data were replaced in the study.
The trial profile is shown in Fig. 1. A1C at follow-up was not obtained for 13 patients, leaving 147 in the ITT population. The CGMS population was based on data collected from 145 patients (CGMS data were incomplete for 15 patients). Some minor differences in mean height, weight, and BMI were seen between the two groups based on receiving BIAsp 30 or BHI 30 first because of the higher proportion of men in the latter group (Table 1).
Insulin dose Mean ± SD total daily insulin doses at the end of the treatment periods were 68.8 ± 37.8 units for BIAsp 30 (median 59.0 [range 6.0238.7]) and 66.6 ± 34.6 units for BHI 30 (58.0 [11.3240.0]). Morning doses were larger than evening doses for both treatments: morning dose 36.0 ± 20.2 units for BIAsp 30 (median 32.0 [range 4120]) vs. 34.6 ± 18.9 units for BHI 30 (32.0 [5130]) and evening dose 33.0 ± 19.0 units (28.0 [2.0118.7]) vs. 32.0 ± 17.4 units (28.0 [4.0110.0]) for BIAsp 30 and BHI 30, respectively.
CGMS At least one episode of IG3.5 was recorded (at any time) by 82% of patients during each treatment period (BIAsp 30 and BHI 30; P = 1.0). For IG2.5, the occurrence was 46 and 54%, respectively (P = 0.28). The percentages of patients that recorded at least one low IG episode (IG3.5 or IG2.5) during daytime and nighttime periods were as follows: 1) daytime occurrence: IG3.5 73% with BIAsp 30 and 70% with BHI 30 (P = 0.60); IG2.5 41% during each treatment (P = 0.10); and 2) nighttime occurrence: IG3.5 51% with BIAsp 30 and 66% with BHI 30 (P = 0.015); IG2.5 25 and 37%, respectively (P = 0.039).
Number of low IG episodes from CGMS Total median values were 3.0 (range 016) vs. 3.0 (020) for BIAsp 30 vs. BHI 30, respectively, and means were 3.76 ± 3.60 vs. 3.93 ± 3.64, respectively (P = 0.62). Daytime median values were 2.0 (013) vs. 2.0 (018) for BIAsp 30 vs. BHI 30, respectively, and means were 2.58 ± 2.79 vs. 2.36 ± 2.67 (P = 0.32). Nighttime median values were 1.0 (08) vs. 1.0 (07) for BIAsp 30 and BHI 30, respectively, and means were 1.18 ± 1.56 vs. 1.62 ± 1.71 (P = 0.011). For IG2.5 episodes, there were no statistically significant differences between treatments (total, day, or night; data not shown). There were also no significant differences in duration of IG3.5 or IG2.5 episodes (total, day, or night) between BIAsp 30 and BHI 30, although nighttime episodes tended to be longer than daytime episodes (data not shown).
Twenty-fourhour distribution of low IG episodes from CGMS
Percentage of time spent with IG <3.5 and <2.5 mmol/l The total percentage of time spent with IG <3.5 or <2.5 mmol/l tended to be lower for BIAsp 30 than for BHI 30, but differences were not statistically significant. In the daytime there were no significant differences between treatments for IG3.5 or IG2.5. At nighttime, the percentage of time spent with IG3.5 or IG2.5 was significantly lower for BIAsp 30 than for BHI 30.
Self-reported hypoglycemia
Rates of self-reported hypoglycemia
Twenty-fourhour timing of hypoglycemic episodes from case report form
Adverse events
A1C and laboratory tests
Diabetes treatment satisfaction
CGMS is a useful tool for assessing daily glucose fluctuations (5) but has certain limitations: It measures glucose concentrations in the extracellular interstitium rather than in the intravascular space. The relationship between glucose concentrations in these two compartments is not straightforward and may alter according to physiological variation in insulin concentration and glucose uptake, utilization, and elimination (6,7). These limitations are countered by the ability to record continuous glucose data and detect unrecognized hypoglycemic episodes (813). Most studies to date have involved patients with type 1 diabetes, and there is relatively little information describing CGMS in type 2 diabetic patients. In the present study, CGMS demonstrated that rates of IG <3.5 and <2.5 mmol/l at night were approximately double those during the day in patients with type 2 diabetes treated with premixed insulins BIAsp 30 and BHI 30. This is contrary to the general perception, based on self-reported data (14,15), that nocturnal hypoglycemia is uncommon in type 2 diabetic patients. Indeed, we also found that in contrast to the CGMS data, self-reported episodes were highest during the day. The majority of nocturnal episodes were therefore unrecognized, although it is unsurprising that patients fail to wake when mildly hypoglycemic at night. There is evidence in type 1 diabetic patients that asymptomatic nocturnal hypoglycemia may induce hypoglycemia unawareness (16), but the clinical relevance of our findings in type 2 diabetic subjects is uncertain. Generally, the distribution of self-reported episodes of hypoglycemia corroborates the CGMS data, increasing our confidence that these findings are robust. The shapes of the two frequency profiles were similar, with both identifying a peak in occurrence of low glucose at lunchtime. However, self-reported episodes at lunchtime were higher during BIAsp 30 treatment than during BHI 30 treatment (opposite to the pattern at night). Thus, there was no overall difference in the frequency of self-reported hypoglycemia. Our CGMS data show that twice-daily BIAsp 30 led to significantly fewer nocturnal episodes of IG <3.5 mmol/l than twice-daily BHI 30. Furthermore, the percentage of time patients spent with IG <3.5 and <2.5 mmol/l at night was lower during treatment with BIAsp 30. Since total daily insulin doses were similar for both insulins, differences in the frequencies of low IG readings may reflect differences in insulin kinetics. The faster onset and shorter duration of the rapid-acting analog, insulin aspart, contained in BIAsp 30 (17,18) may explain the difference in the time of the peak frequency of nocturnal low IG readings, which occurred at 0300 h with BIAsp 30 compared with 0600 h for BHI 30. Self-reported, symptomatic, nocturnal hypoglycemia was also significantly lower with BIAsp 30 than with BHI 30, suggesting that these differences are clinically relevant. The data on the timing of low glucose values in this study may help to guide the dose of premixed insulins containing rapid-acting insulin analogs. Our data suggest that when moving from BHI 30 to BIAsp 30, the prebreakfast dose should be reduced to lower the risk of prelunch hypoglycemia and the predinner dose increased (keeping the overall total insulin dose the same). This should effectively move the ratio of doses toward a 50/50 split, as observed in other recent studies (1921). Furthermore, because of the observed peak in low glucose values at lunchtime, prelunch rather than pre-dinner blood glucose levels may be safer targets for adjusting the prebreakfast dose of a premixed insulin. In conclusion, nocturnal low glucose levels in patients with type 2 diabetes using twice-daily insulin may be more frequent than supposed. The use of BIAsp 30 was associated with similar overall rates of low IG and symptomatic hypoglycemia than BHI 30, but with fewer episodes at night, probably reflecting the longer duration of action of regular human insulin relative to insulin aspart. These data suggest that a more aggressive approach to achieving glucose targets, particularly lower fasting glucose, may be safer when using preparations containing fast-acting insulin analogs.
The following investigators participated in the REACH Study: Dr. J. Alcolado, University Hospital of Wales; Dr. J. Dean, Bolton PCT/Bolton Hospital NHS Trust; Dr. M. Fisher, Glasgow Royal Infirmary; Prof. A. Hattersley, University of Exeter; Dr. S. Heller, Northern General Hospital; Prof. P. Home, University of Newcastle; Dr. D. Hopkins, Central Middlesex Hospital; Dr. R. Jones, St. Thomas's Hospital; Dr. J. Lorains, Clatterbridge Hospital; Dr. P. McNally, Leicester Royal Infirmary; Prof. A. Morris, Ninewells Hospital & Medical School; Prof. T. O'Brien, University College Hospital, Galway; Dr. S. Page, QMC, Nottingham; Prof. R. Donnelly and Dr. A. Scott, Derby City General Hospital; Dr. J. Thow, York District Hospital; Dr. J. Vora, Royal Liverpool University Hospital; Dr. S. Gray, St. John's Hospital; and Dr. D. Bowen-Jones, Arrowe Park Hospital.
For editorial assistance, the authors thank Scott Gouveia.
Published ahead of print at http://care.diabetesjournals.org on 2 February 2007. DOI: 10.2337/dc06-1328. Clinical trial reg. no. ISRCTN34091554, clinicaltrials.gov, and at clinicalstudyresults.org, no. BIASP-1466. Additional information for this article can be found in an online appendix at http://dx.doi.org/10.2337/dc06-1328. P.G.M. has received lectures fees from and been a member of advisory boards for Novo Nordisk. J.D.D. has received honoraria from and been a member of advisory boards for Novo Nordisk. A.D.M. has received renumeration to participate on the speakers bureau of Novo Nordisk and was a clinical trial investigator for the REACH study. P.D.W. receives payment for providing statistical consultancy services to Novo Nordisk. S.R.H. has received fees for giving lectures at symposia sponsored by Novo Nordisk and for participating in research activities sponsored by Novo Nordisk and has served on national and international advisory boards sponsored by Novo Nordisk. Novo Nordisk manufactures and markets the insulin products used in the REACH trial. A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C Section 1734 solely to indicate this fact. Received for publication June 26, 2006. Accepted for publication January 21, 2007.
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