Internet Explorer is no longer supported by Microsoft. To browse the NIHR site please use a modern, secure browser like Google Chrome, Mozilla Firefox, or Microsoft Edge.

Is an intervention ready for HTA researcher-led evaluation?


Published: 10 September 2019

Version: 1.0 - August 2019

Print this document

The Health Technology Assessment (HTA) Programme funds research about the clinical and cost effectiveness and broader impact of healthcare treatments and tests for those who plan, provide, or receive care from the NHS or social care services.

HTA research is undertaken where robust evidence already exists to show that a technology can be effective and where this needs to be compared to the current standard intervention to see which works best. Put simply, HTA study proposals state ‘we know it can work, is safe, and that it can be done in the NHS or social care, but we now want to know whether it works in practice and is cost-effective'.
Given that pragmatic HTA studies require significant public funding, the HTA Programme needs to be convinced that an intervention is ready for HTA researcher-led evaluation. This document outlines issues that may determine this judgement.

Generally, an intervention is ready for HTA evaluation if:

  • there is robust published evidence of efficacy or effectiveness 
  • it has already been tested in a typical NHS or social care setting 
  • there is a reasonable chance it can be delivered and will be used across the NHS or social care in practice if shown to be cost effective

HTA evaluation may also be appropriate if the intervention is already widely used in the NHS or social care, but evidence of benefit, cost effectiveness or harms is lacking.

Is there a reasonable chance of the intervention being effective?

HTA research is undertaken when evidence already exists to show that a technology can be effective. HTA studies usually determine effectiveness and cost effectiveness by testing for a clinically important difference in a primary outcome measure.

The HTA Programme needs to be convinced that the primary outcome effect that the trial is powered to detect is plausible in the light of knowledge of how the intervention works and existing evidence, and that the trial is suitably powered (typically at 90% ) to detect any difference.

All HTA proposals should be preceded by a systematic review of existing literature to determine whether further research is needed.

High quality published systematic reviews may be cited, but these should be supplemented by up-to-date searches for more recent trials. Existing evidence (including studies other than trials) can be used to show that the clinically important difference is plausible. The type of evidence presented will determine whether the case made for HTA funding is convincing:

  • existing trials of effectiveness can provide good evidence to support an HTA trial, especially if meta-analysis of small underpowered trials suggests that the clinically important difference in the primary outcome is plausible
  • existing trials of efficacy can provide evidence to support a proposal for an HTA trial of effectiveness if they show an effect on disease activity that could translate into an important person centred difference in the primary outcome. Efficacy trials are powered to detect differences in measures of disease activity rather than the health or quality of life outcomes used in HTA trials of effectiveness
  • although pilot trials can provide an estimate of the anticipated effect size, the estimate is likely to be imprecise or biased, so they only provide weak evidence to support an HTA trial
  • observational studies showing an association between the intervention and the proposed primary outcome only provide weak evidence to support an HTA trial, regardless of the strength or statistical significance of the association. Such studies are prone to confounding and are only helpful if this risk is addressed convincingly
  • uncontrolled before-versus-after intervention studies are at high risk of bias and only provide very weak evidence for the plausibility of the postulated effect. However, they can provide evidence of deliverability of the intervention in the NHS and acceptability to patients (see below)

The Programme takes into account the potential difficulties in generating the evidence outlined above for some complex interventions. However, there needs to be evidence for the efficacy of its elements and a convincing explanation for how a complex intervention may produce the postulated effect on a health outcome.

Has the intervention been used in typical NHS or social care practice with typical NHS or social care users?

HTA trials determine whether an intervention is effective and cost-effective when delivered in typical NHS or social care settings with typical NHS or social care users. The programme therefore needs to be convinced that the intervention is ready for this type of pragmatic evaluation. This can be achieved by providing evidence from routine data, audit, or small-scale evaluation showing that the intervention can be delivered with reasonable fidelity by typical practitioners and is acceptable to typical patients or users.

Evaluation of fidelity, adherence, and acceptability may form part of the proposed HTA trial, so we do not expect these to be definitively demonstrated before an application is submitted, but there should be a reasonable expectation that they will be achieved. The prior evidence required will depend on the nature of the intervention. A complex intervention or one involving a high level of professional skill or patient involvement will require more evidence than a simple intervention. An intervention that has only ever been used in a very specialist setting or never used in the NHS is unlikely to be considered ready for HTA evaluation. 

Is there a reasonable chance that the intervention (if effective) will be delivered across the NHS or social care?

There are a number of factors, other than effectiveness, which may determine whether an intervention is implemented across the NHS or social care. These include:

  • cost-effectiveness: An expensive intervention may not be cost-effective, according to thresholds for willingness to pay for health gain used by the National Institute for Health and Care Excellence (NICE), even if it is highly effective. The HTA Programme will need to be convinced that this issue has been considered for proposals to evaluate expensive interventions
  • lack of staff or facilities: there may be factors that prevent implementation, such as a lack of specialist staff or facilities across the UK. The programme will need to be convinced that interventions requiring specialist staff and facilities can be delivered across health or social care, if shown to be effective and cost-effective

The intervention is already widely used in the NHS, but evidence of benefit and harms is lacking

If the intervention is already widely used despite a lack of robust evidence of benefit or harm , HTA evaluation offers the potential to reduce unnecessary and potentially harmful intervention. In these circumstances, applicants need to convince the programme that decision-making would be responsive to the evidence produced and would result in major changes to practice – i.e. that an intervention would stop being used for a certain indication, rather than the more usual scenario that an intervention would be introduced for a new indication.

A more complicated scenario involves a proposal intended to show that a cheaper intervention e.g. less intensive physiotherapy or CBT, or one with fewer side effects, has comparable effectiveness to current treatment. In this situation, the programme will need to be convinced that the new intervention has the potential to achieve comparable effectiveness, drawing upon a convincing explanation of how it can deliver this but at lower cost or risk, and that such evidence generated through an HTA study would lead to a change in practice.