The informed consent model assigns patients autonomy over medical interventions and research participation. Where vulnerable patient groups including children and adolescents are concerned, their degree of competence in exercising such autonomy is questionable. Partly because of concerns about the adequacy of consent procedures in vulnerable populations, interest in research into decisional capacity has grown in recent years.
Consent is required for all aspects of medical care, for preventive, diagnostic or therapeutic interventions and research participation. Competence to consent, as we use it in this review, is the clinical concept of the ability of a person to consent to medical interventions or clinical research. The clinical concept of competence may be distinct from the legal one. By law clinicians are required to determine whether patients are competent to give their consent. Strictly speaking, incompetence denotes a legal status that in principle should be determined by a court. Resorting to judicial review in every case of suspected incompetence, however, would very heavily burden both the medical and legal systems; there is therefore good reason to continue the traditional practice of having clinicians determine patients' competence (Appelbaum 1988).
Within the context of daily medical practice, competence is usually assessed implicitly. However, in some clinical settings competence regularly becomes problematic, especially when concerns arise about a person's capacity to make well-considered medical decisions. For example, if a 14-year old boy with acute lymphatic leukaemia is eligible for drug trial participation, how should the researcher examine the competence of his decision to participate in the trial? If a 15-year old boy with germ cell cancer and anaemia expresses his wish not to receive blood transfusion during planned surgery, for religious reasons, is this decision a competent one? A 63-year old man with type 2 diabetes mellitus and schizophrenia is recommended a below-the-knee amputation for peripheral vascular disease but declines; how can his physician assess whether his choice is based on competent decision-making? A woman of 72, living with dementia and anaemia, is recommended to undergo an investigation to trace a location of blood loss, but refuses - is she competent to give informed refusal?
The most extensive and influential research on patients' competence to consent was conducted by the MacArthur Research Network on Mental Health and the Law (Appelbaum 1995), examining competence standards identified by the legal system as relevant to decision-making competence in the USA, UK and many other nations. The four legally-relevant abilities that were addressed were: the ability to state a choice; to understand relevant information; to appreciate the nature of one's own situation; and to reason with information. These four abilities have been generally accepted as the standard for patients' competence to consent in clinical treatment and research practice. Several interview procedures to operationalise these standards and to measure abilities have been developed in recent decades.
The determination of patients’ competence is critical in striking a proper balance between respecting the autonomy of people who are capable of making informed decisions, and protecting those whose abilities are impaired. There is an undeniable need for standardised and accurate competence assessment methods.
Target condition being diagnosed
The target condition we will focus on in this review is patients' competence to consent to medical treatment or clinical research. We will cover groups of patients with and without developmental or mental deficits, or both.
A variety of methods for competence assessment exist, mostly consisting of a structured or semi-structured interview format. Some instruments examine a real-life medical decision, while others are based on clinical vignettes. The instruments include the MacArthur Competence Assessment Tool for Clinical Research (MacCAT-CR), the MacArthur Competence Assessment Tool for Treatment (MacCAT-T), and the Hopkins Competency Assessment Test (HCAT). Content, rating and cut-offs vary between index tests and there is no systematic study on their validity and reliability.
The process of obtaining informed consent starts with providing appropriate information about the proposed medical intervention and alternative options or the scientific research project. An essential element of consent is that informed choices are made voluntarily without coercion or force, and that the person is competent to make such a decision. Starting-points for competence are task and context specificity (Culver 1982). This means that competence should not be conceived as an all-or-nothing judgement implying that the patient is generally competent or generally incompetent. Instead, assessment of competence should be regarded as a specific judgement at a specific moment of whether the patient is able to complete the concrete task that they are facing (Culver 1982). The law imposes a dichotomy (competent versus incompetent) on what, from a clinical perspective, is a spectrum of capacities (Shaw 2001).
In law, competence has traditionally been regarded as a function of age (De Lourdes Levy 2003). The statutory age of majority is generally set at 18 years, although exceptions exist in states or countries worldwide. Competence is presumed present in all adults and is rarely examined as long as the outcomes of decisions concur with the physician's recommendations (Beidler 2001).
Competence to consent may be reduced by several influences such as cognitive impairment, developmental immaturity, certain psychiatric symptoms, and situational factors such as the complexity of the information. Children are deemed competent if they appear to understand information designed for their level of comprehension to an extent appropriate to the nature and scope of the decision. Internationally the statutory age limits differ for clinical research: the lower age limit varies from 7 to 15 years, while the upper age limit is set at 17 or 18 years (Altavilla 2011). Also, for treatment decisions various age limits exist: in some countries autonomous decision-making is lawful only from 18 years onwards, but in other countries minors are allowed to take healthcare decisions from a fixed age below legal majority starting from 12 years (Grisso 1978; Stultiëns 2007). Parents decide for children who are younger than the lower age limit, as these children are considered by definition incompetent to act for themselves. For these children, no actual assessment of competence is necessary. For children between the two age limits, informed consent is required both from children and parents, provided the child is judged competent to decide. Above the designated upper age limit, children are deemed adult in medical decision-making.
In case of incompetence in adults, usually family is allowed to make a proxy decision for general treatment decisions (Saks 2008). In the context of research, laws are less clear, but generally some kind of proxy decision-making is allowed (Saks 2008). In emergency contexts, a person's stress, pain or diminished consciousness may impair their competency. For treatment decisions the most likely result of the informed consent process under these circumstances is 'uninformed trust' (Gammelgaard 2004). Decisions on research participation in the emergency context are a matter of debate; however, formally some kind of proxy decision-making by a legally authorised person is generally allowed (Gammelgaard 2004; Saks 2008).
Possibilities to advance patients' competence rely greatly on improved information provision. Decision aids are developed to provide adult patients and their families with the relevant information about the available options and possible outcomes, to support them in making a decision that is aligned with their preferences. In children decision-making can be facilitated by breaking the process down into smaller but linked choices. Communication difficulties can be overcome by innovative and age-appropriate techniques to convey information (Hein 2012). In conversation, children need clearly-worded information tailored to their comprehension level. It has been found in current practice that communication with parents and children is often flawed, and even that children are not fully informed (Hein 2012).
At present, clinicians tend to make intuitive assessments of children’s and adolescents’ competence, because no standardised method is available to test it objectively. Currently clinicians base their competence judgements on information such as age or school type. It is recognised that age is, at best, a proxy for developmental capacity, and that experience, maturity and psychological state are key determining factors (Hein 2012). In adults, clinicians may not know which standard to apply, and probably use many factors that are not formally recognised in law when assessing their patients' ability to consent to treatment or research (Tan 2001). In older adults and psychiatric patients, clinicians might find it difficult to distinguish between mental status examinations and competence assessment (Vellinga 2004). Several methods of structured competence assessment exist for adults, varying widely in procedure, reliability and validity. However, in the research context few investigators assess understanding of the research protocol and competence prior to accepting consent, and the use of standardised tools is the exception rather than the rule (Kon 2006). Data suggest that the performance of competence assessments is often sub-optimal and hence the reliability of unstructured judgements has been poor. Providing clinicians with the generally accepted legal standards for competence improves their judgements and increases significantly the inter-rater agreement (Appelbaum 2007). These legal standards embody the four capacities: to communicate a choice, to understand the relevant information, to appreciate the medical consequences of the situation, and to reason about treatment choices. Clinicians who are aware of these relevant criteria should be able to assess a patient's competence (Appelbaum 2007).
An assessment measure for competence to consent should have close conceptual relationships with the relevant standards of competence. This implies that more general measures of cognitive abilities like reading ability or Mini Mental State Examination (MMSE) would not be appropriate for a valid test of the specific context-dependent competence to consent to the research or treatment on offer.
This review addresses the following question: which instruments are best qualified to assess patients’ competence to consent to clinical care or research? We will analyse the validity and reliability of the assessment instruments.