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Analytic Hierarchy Process Tested By IQWiG Could Become A Component Of Health Economic Evaluations

It is more important to patients suffering from depression that they show a noticeable response to treatment in the first place than being completely cured. It is exactly the opposite in physicians treating people with this disease: they consider remission to have higher priority than response. This is the result of a pilot project carried out by the German Institute for Quality and Efficiency in Health Care (IQWiG) together with external experts.

Using the example of depression, IQWiG tested whether the () method is in principle suitable to find out which preferences patients have regarding treatment goals. As the pilot project shows, this is the case. An could thus be used in future assessments to aggregate outcome-specific results, that is, results related to individual treatment goals.

Summarize outcome-specific results to an overall value

In its health economic evaluations IQWiG works with a particular method, the efficiency frontier concept. Efficiency frontiers can be drawn either for an aggregated outcome or for a single outcome criterion such as mortality (death rate), morbidity (symptoms and complaints) or quality of life. To combine these efficiency frontiers for different patient-relevant outcomes to an overall evaluation, that is, to aggregate them, the outcome-specific results must be weighted. For this purpose the preferences of patients can, for example, be used.

Involvement of patients has so far been insufficient

In two pilot projects IQWiG has therefore tested the two most widely distributed methods used internationally to determine patient preferences: on the one hand, the AHP, and on the other, the Conjoint Analysis (CA). The report on the AHP is now available.

Patients are in a way the “end-consumers” of medical interventions. Internationally they are therefore involved in the assessments of benefits and costs. However, so far this has not happened in a systematic, transparent and reproducible way. In addition, quantitative approaches such as the AHP method have so far not been used on a regular basis.

Survey includes pairwise comparisons

The example used in the pilot project on AHP was pharmaceutical treatment of depression. Antidepressants are also the subject of the IQWiG’s first health economic evaluation. The structured interviews were held in groups, separated according to patients and physicians. The questions addressed different dimensions of benefit and harm: effectiveness (response, remission, avoidance of relapse), avoidance of side effects as well as impact on quality of life. A response is regarded to be achieved when the score for the manifestation of symptoms, measured by means of a depression scale, can be halved. In contrast, remission requires the patient to be free of symptoms.

In the survey participants were to decide which of two criteria in a series of pairwise comparisons seemed more important to them – for example, whether it would be more important to them for a drug to reduce either anxiety or pain. Respondents could specify how much more important a criterion was to them by means of a scale ranging from -9 to +9. IQWiG then calculated the weight of each outcome criterion from the results of the pairwise comparisons.

Remission is more important to physicians than to patients

The results showed that patients with depression in part have clearly different preferences than treating physicians. Out of a total of 11 outcome criteria both groups identified the same six criteria as the most important ones. However, the weights were distributed very differently between these six criteria. For instance, response to treatment was weighted the highest by patients whereas remission, i.e. the disappearance of symptoms related to depression, was most important to physicians. Remission was only ranked in sixth place by patients; conversely, response was ranked in fifth place by physicians.

Group discussion illuminates background and motives

What prompted the respondents to weight outcomes one way and not the other was the subject of the group discussion held after each question-and-answer session on a paired comparison. Some differences can be explained thanks to the additional information obtained: according to this, patients, in contrast to physicians, weighted “response” the highest as they perceived the state of acute depression to be so unbearable that they regarded initial relief from this condition as the paramount treatment goal.

This does not mean that they do not want to achieve remission; however, they see this as a distant goal that is, if at all, difficult to achieve. One patient summed it up as follows “I would rather live with mild depression for the rest of my life than have no hope that a drug will give me some relief in the acute state of depression.”

AHP is manageable for patients

After this pilot project with a small number of participants, IQWiG assesses the AHP to be a basically suitable and manageable method. “Patients can handle the procedure and it delivers useful results. One could thus employ the AHP method for weighting outcomes. In principle this applies to benefit assessments as well as to health economic evaluations,” says Andreas Gerber-Grote, Head of IQWiG’s Health Economics Department.

Methodological challenges of AHP

However, a number of challenges have to be overcome for practical implementation. For instance, the interview has to be structured in such a way that outcome criteria do not overlap, for example that questions referring to “anxiety” are not asked more than once. This would inevitably lead to a higher weighting of this aspect.

In addition, it needs to be clarified beforehand who is to be questioned: patients, physicians or – as in the United Kingdom – a sample of the general population? In any case those questioned ought to be selected in a representative manner. One would also have to determine which degree of precision is required, that is, how robust the results need to be. This is because the higher the demands, the more people have to be questioned and the greater the overall effort required for the AHP.

Process of report production

IQWiG has published the results of its work, prepared in cooperation with external experts, in the form of a working paper. Working papers are prepared under the Institute’s own responsibility, without requiring a commission by the Federal Joint Committee (G-BA) or Federal Ministry of Health. They either aim to provide information on developments relevant to health care or, as in the present case, originate during the development of the Institute’s methods. The document was sent to the G-BA on 8 May 2013.


Institute for Quality and Efficiency in Health Care