If the Numbers Don't Fit... Discrepancies Between Glucose Meter Readings and Hemoglobin A1c Reveal Stress of Living With Diabetes
C.S. is a 17-year-old girl who has had type 1 diabetes for 14 years. During early childhood, her hemoglobin A1c (A1C) was usually < 8%, and her mother performed most of her diabetes care tasks. As she entered adolescence, C.S. took on more of the diabetes care herself and shared less of the management responsibilities with her mother. She used glargine once a day and lispro multiple times each day. She used a formula to calculate her insulin dose based on her carbohydrate intake (1 unit for each 10 g of carbohydrate eaten) and a correction factor for high glucose concentrations (1 unit for each 50 mg/dl above 100 mg/dl). She had been using this plan for 2 years.
At a recent diabetes clinic visit, she reported being satisfied with her glycemic control, and the average on her glucose meter memory was 147 mg/dl. In downloading her meter records, her providers noted at least 3-4 glucose tests each day, almost all within the 70-180 mg/dl range. Her A1C measured on the same day, however, was 9.4% (normal 4-6%).
After lengthy discussion with her about this discrepancy, C.S. admitted that she had used control solution in place of her own blood for most of the glucose meter checks. Control solution is part of the glucose meter kit and is used to confirm the accuracy of the machine and test strips. Results using control solution usually are close to the normal range (the expected range is indicated on the control solution bottle) as long as the machine and test strips are working properly.
C.S. complained of being tired of dealing with her diabetes and said she found it “exhausting” to meet the expectations of her family and diabetes team. Her mother, who accompanied her to all the clinic visits, was surprised by C.S.'s use of control solution. The mother reported having little involvement in her daughter's diabetes daily management in recent years since C.S. wanted to be independent and seemed to have things “under control.” Diabetes had become a source of tension between them, with C.S. feeling that her mother was nagging her, and her mother feeling excluded from the management decisions.
What are the causes of discrepancies between glucose meter numbers and the average reflected by A1C results?
Why would an adolescent manipulate the numbers on a glucose meter?
How can providers help with control and coping issues in adolescents with diabetes?
This case exemplifies a number of issues that arise when dealing with adolescents with diabetes. A1C is an important tool for evaluating glycemic control and directly relates to risk for long-term microvascular complications.1 When obtained in the office setting at the time of a visit, as is possible with newer devices such as the DCA2000 (Bayer), A1C can be used to guide discussion at the visit. Alternatively, A1C can be drawn in a laboratory before the clinic visit, so that results are available at the time of the face-to-face meeting. In this case, the A1C was helpful in noting the discrepancy with numbers recorded on the glucose meter.
Such discrepancies may occur for a number of reasons. The glucose meter values are only individual points in time and may not detect fluctuations in glucose, especially postprandially and overnight. Checking glucose more frequently or using continuous glucose monitoring may help detect otherwise unnoticed hyperglycemia.2 In addition, glucose meters need to be calibrated with a code from the test strip, and if the wrong code is entered, the numbers may be inaccurate. Test strips need to be protected from light and can become damaged, leading to unreliable measurements.
Hematological conditions can also affect the accuracy of the A1C measurement. A1C typically reflects the glucose concentration over the past 3 months, with ∼ 50% determined by metabolic control during the past month. Conditions that shorten the lifespan of the red blood cell, such as hemolytic anemia, may falsely lower the A1C measurement.3 In beta-thalassemia, the presence of HbF may result in falsely elevated A1C measured by immunoassay, which is the method used in most office A1C machines.4 The effect of these conditions on A1C measurement and the utility of the fructosamine measurement are reviewed in a recent issue of Clinical Diabetes.5
The discovery of a discrepancy between the A1C and glucose meter readings provides an opportunity to explore the patient's feelings about diabetes and the daily management routine. Most youth with diabetes experience worsening in their metabolic control during adolescence. This change is related in part to changes in the hormonal milieu, especially with an increase in growth hormone secretion serving to undermine insulin sensitivity. In addition, a number of psychosocial and developmental issues come into play: perceptions about body image develop, privacy and independence become important, and limit testing often challenges parent-adolescent relationships.
Adolescents cope with the stress of chronic illness in different ways. Emotion-focused coping strategies, such as behavioral and mental disengagement, are associated with poor metabolic control and reduced diabetes-related quality of life.6 In contrast, active coping strategies, such as seeking out more information about treatment and being involved in decision-making, are associated with lower A1C results.7 However, patients with poor glycemic control often experience negative feedback about their management, and this in and of itself may be the reason for disengagement. Parental concern can be expressed as anger and outrage, leading to a vicious cycle of deceit and shame for the patient. Not surprisingly, family conflict about diabetes is associated with poorer glycemic control.8
Although it is tempting to console families by telling them that their adolescent's difficulties with diabetes are likely to be temporary or just a passing phase, there is recent evidence that this is not the case. Bryden et al.9 reported worse-than-expected clinical and psychiatric outcomes in approximately one-third of all young adult patients with diabetes. The authors suggested that much earlier identification of psychiatric and behavioral issues is needed, since symptoms in adolescence were predictive of later psychiatric disorders.
The negative cycle can be interrupted. Involving the family and discussing their concerns about the patient's diabetes can help dispel some of the fear and anxiety surrounding the numbers. Treating the numbers as information in a nonjudgmental manner can remove the negative emotional aspect of diabetes management. Identifying and treating psychiatric disorders is likely to affect long-term outcome. And, teaching coping skills to adolescents is effective, resulting in lower A1C results, better diabetes and medical self-efficacy, and less impact of diabetes on quality of life.10
While adolescents may desire independence from their parents, they likely do not have the maturity to handle every aspect of diabetes alone. Family-focused teamwork intervention is associated with improved A1C in children and adolescents with diabetes.11,12 In order to eliminate the perception of nagging on the part of the parent, some families have a set time in the evenings to review the glucose meter numbers. The parent's role may be recording the numbers in a logbook or helping the adolescent look for patterns in the logbook so that the insulin regimen can be modified if necessary. Some adolescents want a break from diabetes for a day, and the parent can take over the diabetes care for this period of time.
In this case, discussion during the clinic visit led to the patient's confession that she had falsified the glucose meter numbers. Although most patients likely would not readily admit to this, beginning the discussion about living with diabetes may uncover surprising revelations regarding coping skills and sense of personal control. Recognizing the issue is the first step, and a multidisciplinary approach is necessary to address the complicated issues that diabetes presents. Input from a psychologist, social worker, or psychiatrist consultant is often helpful. Removing the pressure of judgment about the glucose meter numbers while still involving the family in the diabetes care, involving the patient in diabetes management decisions, developing realistic treatment goals, and discussing coping methods are important strategies to help adolescents live successfully with diabetes.
Glucose meters can be manipulated to make it appear that numbers are in the target range.
Hematological conditions can result in discrepancies between A1C results and glucose meter readings.
Differences in glucose meter readings, written logbooks, and A1C results may be a sign of underlying stress and difficulty dealing with expectations about diabetes management.
Worsening glycemic control during adolescence may reflect hormonal as well as psychosocial and developmental changes.
Encourage interdependence rather than independence for adolescents with diabetes, and stress ongoing parental involvement.
A multidisciplinary approach is essential for helping adolescents with diabetes.
Susan C. Conrad, MD, is a pediatric endocrinologist at Children's Hospital and Research Center at Oakland in Oakland, Calif. Stephen E. Gitelman, MD, is a professor of clinical pediatrics in the Department of Pediatric Endocrinology at the University of California, San Francisco.
- American Diabetes Association