Genetic testing in diabetes: Not just a question of risk

M.Shepherd, A.T.Hattersley, A.C. Sparkes

Paper presented at the Qualitative Evidence-based Practice Conference, Coventry University, May 15-17 2000.

Abstract

Genetic testing is now possible in maturity-onset diabetes of the young (MODY), an unusual genetic subtype of diabetes. However the implications of genetic testing in diabetes have not been studied. Adopting a social constructivist stance this paper compares and contrasts the multiple meanings of genetic testing in diabetes to those involved]. Data is presented from case studies of four MODY families who received diagnostic genetic test results, Two also had predictive genetic tests in their children. In-depth interviews were conducted with 16 family members and 7 health care professionals. Content analysis highlighted 3 dominant themes; personal experience of diabetes, views of genetic information / lay beliefs and the impact of genetic test results. 3 unique elements also emerged; varied views of predictive testing, differences in perceptions about a rare condition and difficulties communicating with professionals. Genetic testing in MODY should be provided with an awareness of family’s lay beliefs and personal experiences of diabetes. Although professionals consider communicating genetic risk to be important, families had other priorities. These findings have implications for the provision of genetic testing in diabetes.

Introduction

Diabetes is a chronic illness that affects 1.4 million people in the United Kingdom]. Maturity-onset diabetes of the young (MODY) is a rare subtype of diabetes caused by a mutation in a single gene [Hattersley, 1998 #89]. It is characterised by a young onset, non-insulin dependent diabetes and autosomal dominant inheritance and affects 1% of those with diabetes [Appleton, 1996 #4]. Diagnostic and predictive genetic testing is now possible for 80% of MODY families. Diagnostic tests for those with diabetes, allows the diagnosis to be confirmed and specific guidance regarding treatment and prognosis to be provided. Predictive genetic tests are also possible for family members not known to have diabetes. This identifies whether they have inherited an affected gene and have an increased risk of developing diabetes or not. Despite these technological advances there has been little research into the implications of genetic testing in diabetes [Shepherd, 2000 #118].

The families

All four families had previously recieved diagnostic genetic test results and were identified as interesting cases from whom we could increase our understanding of the implications of genetic testing in diabetes.

  • Family 1 - the first family in the UK who requested a predictive test. Bob1 was diagnosed with diabetes at 26 years. His father and sister both had diabetes and she died young as a result. Bob’s oldest daughter was diagnosed with diabetes at 11 years. Diagnostic genetic testing revealed mutations in HNF1 in Bob and Kim. The family subsequently requested a predictive test in their younger daughter aged 5.
  • Family 2 - had a family history of 5 generations of diabetes. The family had strong lay beliefs about genetics and the inheritance of MODY. Sharon, was diagnosed with diabetes during her 1st pregnancy and her youngest son was diagnosed at 6 years. 12 other family members had raised blood glucose levels. A mutation in the glucokinase (GCK) gene was identified. Sharon was concerned about the implications of MODY which she believed caused her sons disruptive behaviour.
  • Family 3 - the first family in the UK to be identified with HNF1. This is associated with renal dysfunction. Fiona had a therapeutic termination for her first pregnancy as ultrasound indicated bilateral cystic kidneys. In her second pregnancy Fiona was diagnosed diabetic and found to have two renal cysts, her son, Toby, was found to have one non-functioning kidney. . No other family members had diabetes or renal problems. Following identification of HNF1 in Fiona, she requested a predictive test in Toby, aged 18 months
  • Family 4 - had another rare form of MODY, HNF4. Wendy, was diagnosed diabetic at 20 years and her mother, Betty, had been diagnosed at 15 years. No other family members had been diagnosed diabetic. Wendy had one daughter, Louise, aged 5, but decided against a predictive genetic test.

Methods

All individuals were contacted by the lead researcher to discuss the project and the ethical principles should they become involved. In-depth interviews were conducted with 16 individuals from these 4 MODY families; 10 had been identified with gene mutations which had caused their diabetes and 6 were unaffected. 7 health care professionals from the diabetes and genetics teams involved were also interviewed. Interviews lasted approximately 1 hour and written consent was obtained. The focus of the interviews was broad, asking participants to discuss their experiences of diabetes and genetic testing. Interviews were tape recorded and transcribed verbatim, then subjected to content analysis. Reflective notes were also made by the lead researcher about the interview itself, any discussion after the interview and her feelings about the interaction. The transcripts were then read several times and narrative segments and categories were identified. Data from individual family members was then collated into a case study of each family. The four case studies were then compared and contrasted to highlight common issues and areas of difference.

Results

Qualitative analysis and comparison of the cases highlighted three dominant themes i) strong influence of personal experience of diabetes, ii) views of genetic information / lay beliefs and iii) the impact of diagnostic genetic test results. Three unique elements also emerged i) varied views of predictive testing, ii) differences in perception of having a rare condition and iii) difficulties communicating with health care professionals.

Dominant themes

1. Personal experience of diabetes strongly influenced perceptions and acceptance of the disease.

a) The impact of the diagnosis. All families described the shock they felt at diagnosis. Chronic illness is recognised as an assault on a persons sense of identity and this may affect their sense of self. The impact of the diagnosis in those with a family history may be traumatic due to their previous experience of the disease

b) Acceptance of the diagnosis; Acceptance of the diagnosis varied drammatically and was influenced by many factors. Coming to terms with the diagnosis involves understanding and accepting the on-going nature of chronic illness and its biographical consequences.

c) Personal loss resulting from the diagnosis; In all cases the diagnosis of diabetes resulted in personal loss. Individuals are often acutely aware of their previously ‘taken for granted’ aspects of self when they are no longer attainable, this leads to the loss of self.

d) Disclosing diabetes to others; There were marked differences regarding willingness to disclose diabetes to others. Many people with chronic illness wish to lead conventional lives and have concerns about disclosing their illness

e) Negative autobiographical memories; Three families had previous experience of diabetes complications in other family members. Such traumatic experiences can have serious implications for individuals and can change the meaning of their life

f) Need to normalise diabetes The need to normalise diabetes was strong. The way families with chronic illness ‘normalise’ affected members and daily life is the preferred story for many families

2. Views of genetic information / evidence of lay beliefs

Genetic information about risk was regarded by the families as too complicated and unimportant, they had other priorities. Genetic information and estimates of risk may be key issues for counsellors but not families. There were strong lay beliefs and misconceptions regarding genes and the inheritance of MODY. Such lay knowledge may conflict with information provided by professionals and perceptions of health threats may be linked to individuals own models of inheritance.

3. The impact of diagnostic genetic test results

The impact of the genetic results varied tremendously. Prior experiences may affect individuals responses to genetic testing in terms of psychological outcomes, although feelings of guilt are common

Unique elements

1. Varied views of predictive testing

Two requests for predictive tests were instigated by the affected parents. Desire to reduce uncertainty and personal experience frequently motivates families to request predictive tests. Gradually introducing a child to the idea they will develop a disease has been considered a valid reason for performing predictive tests. However there has also been concern regarding the possible emotional consequences of inappropriately labelling children at risk as sick. It has been suggested that parents are in better position than professionals to decide whether predictive testing is appropriate.

2. Differences in perception of having a rare condition

The effect of realising their diabetes was rare had varied consequences. The choice of words used may affect how families view the diagnosis.

3. Difficulties communicating with health care professionals;

Communication with health care professionals was a key issue for three families, however their concerns varied. The potential mismatches between families and professionals priorities has previously been recognised, however greater understanding of patients illness narratives could improve communication.

Discussion / Conclusion

These four case studies of genetic testing in diabetes provide insights into the perspectives of families and health care professionals involved. They provide important lessons for the future provision of genetic testing in diabetes which should be provided with an awareness of the family’s lay beliefs and personal experiences of diabetes. Lay beliefs regarding inheritance and the causes of diabetes were common. Genetic information is considered by families to be too complicated. Families priorities regarding genetic information should be identified so these can be adequately addressed as information about risk is a priority for professionals, but not patients. Risk assessment may be one factor influencing decisions regarding genetic testing however this paper has demonstrated that where such concerns exist they are connected to a range of other issues that shape the decision making process.