Consent to antipsychotic drugs and tardive dyskinesia after Chester v Afshar

Introduction

Consent is defined in the Mental Health Act 1983 Code of Practice ¹ as follows:

‘Consent is the voluntary and continuing permission of a patient to be given a particular treatment, based on a sufficient knowledge of the purpose, nature, likely effects and risks of that treatment, including the likelihood of its success and any alternatives to it.’

A patient may be deemed to have given valid consent providing the doctor can show that he has explained to the patient, in broad terms, the nature and effect of the treatment. ² A doctor has a further duty of care towards every patient to give adequate information about the risks of that treatment for that patient. The amount of information the doctor had to give to the patient to successfully defend a claim in negligence used to be decided by reference to how much information a responsible body of fellow practitioners in that specialty would give (the Bolam test). ³ This issue was discussed in great detail by the five Law Lords in the Sidaway case in the House of Lords. ⁴ The case law from the USA and Canada in relation to informed consent was reviewed. All five Law Lords dismissed the appeal by Mrs Sidaway on the facts of the case. Three of the Law Lords stated that the amount of information to be given by the doctor should be decided by the Bolam test. Lord Templeman argued that doctors should give details of all material risks of a proposed treatment to allow a patient to make a balanced judgment if they choose to make a balanced judgment but emphasised that doctors have a therapeutic privilege in deciding how much information to give individual patients. Lord Templeman also stated the court could award damages against the doctor if it (the court) decided that the doctor had not given sufficient information. Lord Scarman explained how ‘material risks’ are determined by the ‘prudent patient’ test as follows:

‘a risk is … material when a reasonable person, in what the physician knows or should know to be the patient's position, would be likely to attach significance to the risk or cluster of risks in deciding whether or not to forego the proposed therapy…’

quoting from the US case of Canterbury v Spence (1972) 464F 2d 772 at page 787, the origin of the informed consent doctrine. Lord Scarman was alone in arguing that this doctrine pertains in English Law. He argued that doctors should explain to patients the probability of each risk or side-effect, the seriousness of the injury resulting from the risk and whether the risk is general to that type of treatment or specific to the very specific procedure or treatment this doctor is recommending for this patient. He did accept that the doctor could withhold information about a risk (invoke the therapeutic privilege) if he, the doctor, could show he reasonably believed that telling that patient of that risk would be detrimental to that patient's physical or mental health. Lord Bridge mentioned a risk of 10% chance of a grave adverse consequence of a surgical procedure as being so high that the patient would need to be made aware of it.

As things stand, the doctrine of full informed consent to treatment has not been accepted by the English Courts. Doctors are obliged to give details of common or severe side-effects of a proposed treatment unless they wish to invoke therapeutic privilege. Recent General Medical Council guidance ⁵ emphasizes the partnership approach between doctors and patients and the need for doctors to give at least basic information about possible side-effects of treatment. The guidance does not outrule therapeutic privilege totally, stating the doctor may withhold information if he believes giving the information would cause the patient serious harm.

The judgment in Chester v Afshar

Miss Chester suffered from persistent back pain. She approached Mr Afshar, a consultant neurosurgeon. He recommended surgical treatment. He did not mention the risk of cauda equina syndrome other than as a throwaway line that he had never crippled anyone yet. He performed the surgery without negligence three days later. When she recovered she was suffering from cauda equina syndrome, which has a risk of occurring without negligent operating procedure of 1–2% with that operation. Miss Chester argued that if she had been warned of the frequency and severity of this complication, she might not have had the surgery performed when she did, shortly after her initial consultation with Mr Afshar, but would have sought a second and possibly a third opinion. Miss Chester did not say that she would never have had the surgery which Mr Afshar was recommending and accordingly she could not prove, on the balance of probabilities, that her injuries resulted from the act or omission of the surgeon by the usual standard of causation in medical negligence cases. Three of the five Law Lords agreed that her claim should succeed on policy grounds. ⁶ They explained that because she had not been given the full information about this non-negligent inherent risk of the treatment, she had been prevented from making a fully-informed decision. Therefore, she was entitled to damages when this particular adverse event occurred. This judgment caused immediate consternation in legal circles. ^7–9 The NHS Litigation Authority sent a warning ¹⁰ to all NHS Trusts about the implications of the judgment. There is still uncertainty for clinicians to know which risks to tell patients. To quote Kay Wheat ¹¹ : ‘The judgments in this case are startling in their lack of clarity on this point’. She continues by stating that the only safe (but impractical) way is to inform patients of any and all risks that are more than transient. Other authors have suggested other standards of information disclosure: ‘We suggest that the duty to inform about risk goes further and must encompass not only the perspective of the reasonable patient, but also the perspective of each particular patient’. ¹² The underlying reasons for the decision have been criticized as making bad law in a comprehensive comparison with the judgment in another recent medical negligence case Gregg v Scott. ¹³ During 2006, about 10% of new clinical negligence claims have concerned allegedly negligent advice given to patients. ¹⁴

Tardive dyskinesia

Dyskinesia is characterized by abnormal involuntary movements which are particularly noticeable in the buccolingual-masticatory musculature but may also affect the limbs and trunk. It may occur for no known reason (spontaneous) or be a delayed side-effect to taking antipsychotic drugs (tardive).

Spontaneous dyskinesia was reported as occurring in 1.3% of healthy elderly people and in 4.8% of medical geriatric inpatients. ¹⁵ Prospective studies of the incidence of tardive dyskinesia (TD) in adults taking neuroleptic medications have shown an incidence of 24% of new cases after seven years ¹⁶ and 20% after five years. ¹⁷ One study of hospitalized patients with chronic schizophrenia reported rates of about 50% prevalence of TD in both those patients treated with antipsychotic drugs and the smaller group of patients who had never received antipsychotic drugs. ¹⁸ Patients who develop TD have a higher rate of morbidity and mortality than patients treated with antipsychotic drugs who do not develop TD. ^19,20

Patients who take antipsychotic drugs have a higher incidence of TD than the incidence of spontaneous dyskinesia in the general population. However, for an individual patient with schizophrenia it cannot be said with 100% confidence that they would not develop spontaneous dyskinesia whether or not they take antipsychotic drugs.

Appropriate information about risk of tardive dyskinesia

TD is a material risk to all patients prescribed antipsychotic drugs for the treatment of schizophrenia. This risk should be explained to the patient at the time of initiation of therapy, if they have capacity. If the patient does not have capacity, the prescribing doctor must weigh up all the risks and benefits of treatment and make a decision in the patient's best interests. When the patient regains capacity, their consent for the treatment must be sought. All antipsychotic drugs may cause TD but there is a body of research evidence showing that the first generation antipsychotics have a higher incidence of this adverse event than the second generation drugs. ²¹ Within three years of commencing antipsychotic drug treatment this differential incidence of TD will result in a 10% difference in prevalence of the disorder in working-age adults. I argue, therefore, that this differential incidence has become a material fact which the patient should know about.

The study by Leucht et al. ²² shows that there may be no significant difference in the incidence of extra-pyramidal side-effects, in general, between second generation antipsychotics and low potency first generation antipsychotics. There has not been enough long-term follow-up studies of patients with schizophrenia exposed only to one single atypical antipsychotic to quantify the risk of TD developing with each atypical. ²³ This lack of studies means that doctors cannot give the specific information which patients may request about individual antipsychotic drugs.

Conclusions

The limitations of current knowledge and the uncertainties about incidence of spontaneous versus TD must be explained to patients to gain informed consent to treatment with antipsychotic drugs. The failure to give such advice was one of the minor issues in the successful claim for damages for prescribing an antipsychotic drug reported in this journal in 2007. ²⁴ The benefits of treatment with antipsychotic drugs must also be explained to the patient. Antipsychotic drugs are an essential part of the treatment of the symptoms of schizophrenia. All effective antipsychotics appear to work on dopamine systems in the brain, ²⁵ with the consequent risk of leading to TD symptoms with long-term usage. Antipsychotic drug treatment may be given to patients without their consent in certain circumstances under statute law (Mental Health Act 1983 as amended in England and Wales). TD is only one of the side-effects linked to antipsychotic drug treatment. Patients must also be informed about risks of weight gain, hyperlipidaemia, diabetes mellitus and extra-pyramidal side-effects. The patient and psychiatrist must then make a joint decision about treatment with antipsychotic drugs. This risk of developing TD cannot be eliminated. The patient must be monitored clinically for the development of early signs of TD (plus blood tests to monitor hyperlipidaemia, etc). This monitoring must be continued as long as the patient is taking antipsychotics. The question of which healthcare professional does this monitoring, must be decided locally but it is imperative that the patient receives the monitoring and the ongoing review of the need for continued antipsychotic treatment. This close monitoring of the patient will ensure the patient only receives necessary treatment, the risk of developing TD is managed and the litigation risk to the professional is minimized.