Influence of number needed to treat, costs and outcome on preferences for a preventive drug

Patient preferences for cardiovascular preventive medication: a systematic review

OBJECTIVE

To systematically review current evidence regarding the minimum acceptable risk reduction of a cardiovascular event that patients feel would justify daily intake of a preventive medication.

METHODS

We used the Web of Science to track the forward and backward citations of a set of five key articles until 15 November 2016. Studies were eligible if they quantitatively assessed the minimum acceptable benefit-in absolute values-of a cardiovascular disease preventive medication among a sample of the general population and required participants to choose if they would consider taking the medication.

RESULTS

Of 341 studies screened, we included 22, involving a total of 17 751 participants: 6 studied prolongation of life (POL), 12 studied absolute risk reduction (ARR) and 14 studied number needed to treat (NNT) as measures of risk reduction communicated to the patients. In studies framed using POL, 39%-54% (average: 48%) of participants would consider taking a medication if it prolonged life by <8 months and 56%-73% (average: 64%) if it prolonged life by ≥8 months. In studies framed using ARR, 42%-72% (average: 54%) of participants would consider taking a medication that reduces their 5-year cardiovascular disease (CVD) risk by <3% and 50%-89% (average: 77%) would consider taking a medication that reduces their 5-year CVD risk by ≥3%. In studies framed using 5-year NNT, 31%-81% (average: 60%) of participants would consider taking a medication with an NNT of >30 and 46%-87% (average: 71%) with an NNT of ≤30.

CONCLUSIONS

Many patients require a substantial risk reduction before they consider taking a daily medication worthwhile, even when the medication is described as being side effect free and costless.

Communicating treatment effectiveness in the context of chronic disease processes

A better understanding of the risk concept in relation to treatment of chronic disease processes is warranted. Consequences of therapies may be described in terms of risk reductions or postponement of adverse outcomes. This review argues that for most interventions, neither of these measures adequately characterize the distribution of treatment benefit across patients. More focus should be placed on choosing the context-relevant outcome measure and on developing techniques for extracting and communicating 2D outcome measures where the distribution of outcomes across patients is explicitly reflected. Since the distribution of outcomes affects patients' valuation of interventions, more research into risk communication is likely to lead to improved decision making.

Using alternative statistical formats for presenting risks and risk reductions

BACKGROUND

The success of evidence-based practice depends on the clear and effective communication of statistical information.

OBJECTIVES

To evaluate the effects of using alternative statistical presentations of the same risks and risk reductions on understanding, perception, persuasiveness and behaviour of health professionals, policy makers, and consumers.

SEARCH STRATEGY

We searched Ovid MEDLINE (1966 to October 2007), EMBASE (1980 to October 2007), PsycLIT (1887 to October 2007), and the Cochrane Central Register of Controlled Trials (The Cochrane Library, 2007, Issue 3). We reviewed the reference lists of relevant articles, and contacted experts in the field.

SELECTION CRITERIA

We included randomized and non-randomized controlled parallel and cross-over studies. We focused on four comparisons: a comparison of statistical presentations of a risk (eg frequencies versus probabilities) and three comparisons of statistical presentation of risk reduction: relative risk reduction (RRR) versus absolute risk reduction (ARR), RRR versus number needed to treat (NNT), and ARR versus NNT.

DATA COLLECTION AND ANALYSIS

Two authors independently selected studies for inclusion, extracted data, and assessed risk of bias. We contacted investigators to obtain missing information. We graded the quality of evidence for each outcome using the GRADE approach. We standardized the outcome effects using adjusted standardized mean difference (SMD).

MAIN RESULTS

We included 35 studies reporting 83 comparisons. None of the studies involved policy makers. Participants (health professionals and consumers) understood natural frequencies better than probabilities (SMD 0.69 (95% confidence interval (CI) 0.45 to 0.93)). Compared with ARR, RRR had little or no difference in understanding (SMD 0.02 (95% CI -0.39 to 0.43)) but was perceived to be larger (SMD 0.41 (95% CI 0.03 to 0.79)) and more persuasive (SMD 0.66 (95% CI 0.51 to 0.81)). Compared with NNT, RRR was better understood (SMD 0.73 (95% CI 0.43 to 1.04)), was perceived to be larger (SMD 1.15 (95% CI 0.80 to 1.50)) and was more persuasive (SMD 0.65 (95% CI 0.51 to 0.80)). Compared with NNT, ARR was better understood (SMD 0.42 (95% CI 0.12 to 0.71)), was perceived to be larger (SMD 0.79 (95% CI 0.43 to 1.15)).There was little or no difference for persuasiveness (SMD 0.05 (95% CI -0.04 to 0.15)). The sensitivity analyses including only high quality comparisons showed consistent results for persuasiveness for all three comparisons. Overall there were no differences between health professionals and consumers. The overall quality of evidence was rated down to moderate because of the use of surrogate outcomes and/or heterogeneity. None of the comparisons assessed behaviourbehaviour.

AUTHORS' CONCLUSIONS

Natural frequencies are probably better understood than probabilities. Relative risk reduction (RRR), compared with absolute risk reduction (ARR) and number needed to treat (NNT), may be perceived to be larger and is more likely to be persuasive. However, it is uncertain whether presenting RRR is likely to help people make decisions most consistent with their own values and, in fact, it could lead to misinterpretation. More research is needed to further explore this question.

What are effective strategies to communicate cardiovascular risk information to patients? A systematic review

OBJECTIVE

To compare different interventions used to communicate cardiovascular risk and assess their impact on patient related outcomes.

METHODS

A systematic search of six electronic data sources from January 1980 to November 2008. Data was extracted from the included studies and a narrative synthesis of the results was conducted.

RESULTS

Fifteen studies were included. Only four studies assessed individuals' actual cardiovascular risk; the rest were analogue studies using hypothetical risk profiles. Heterogeneity in study design and outcomes was found. The results from individual studies suggest that presenting patients with their cardiovascular risk in percentages or frequencies, using graphical representation and short timeframes, is best for achieving risk reduction through behaviour change. However, this summary is tentative and needs further exploration.

CONCLUSION

Better quality trials are needed that compare different risk presentation formats, before conclusions can be drawn as to the most effective ways to communicate cardiovascular risk to patients.

PRACTICE IMPLICATIONS

Instead of directing attention to the accuracy of cardiovascular risk prediction, more should be paid to the effective presentation of risk, to help patients reduce risk by lifestyle change or active treatment.

Joint and Separate Evaluation of Risk Reduction

Background. When people make choices, they may have multiple options presented simultaneously or, alternatively, have options presented 1 at a time. It has been shown that if decision makers have little experience with or difficulties in understanding certain attributes, these attributes will have greater impact in joint evaluations than in separate evaluations. The authors investigated the impact of separate versus joint evaluations in a health care context in which laypeople were presented with the possibility of participating in risk-reducing drug therapies. Methods. In a randomized study comprising 895 subjects aged 40 to 59 y in Odense, Denmark, subjects were randomized to receive information in terms of absolute risk reduction (ARR), relative risk reduction (RRR), number needed to treat (NNT), or prolongation of life (POL), all with respect to heart attack, and they were asked whether they would be willing to receive a specified treatment. Respondents were randomly allocated to valuing the interventions separately (either great effect or small effect) or jointly (small effect and large effect). Results. Joint evaluation reduced the propensity to accept the intervention that offered the smallest effect. Respondents were more sensitive to scale when faced with a joint evaluation for information formats ARR, RRR, and POL but not for NNT. Evaluability bias appeared to be most pronounced for POL and ARR. Conclusion. Risk information appears to be prone to evaluability bias. This suggests that numeric information on health gains is difficult to evaluate in isolation. Consequently, such information may bear too little weight in separate evaluations of risk-reducing interventions.

Calculation of NNTs in RCTs with time-to-event outcomes: a literature review

Background

The number needed to treat (NNT) is a well-known effect measure for reporting the results of clinical trials. In the case of time-to-event outcomes, the calculation of NNTs is more difficult than in the case of binary data. The frequency of using NNTs to report results of randomised controlled trials (RCT) investigating time-to-event outcomes and the adequacy of the applied calculation methods are unknown.

Methods

We searched in PubMed for RCTs with parallel group design and individual randomisation, published in four frequently cited journals between 2003 and 2005. We evaluated the type of outcome, the frequency of reporting NNTs with corresponding confidence intervals, and assessed the adequacy of the methods used to calculate NNTs in the case of time-to-event outcomes.

Results

The search resulted in 734 eligible RCTs. Of these, 373 RCTs investigated time-to-event outcomes and 361 analyzed binary data. In total, 62 articles reported NNTs (34 articles with time-to-event outcomes, 28 articles with binary outcomes). Of the 34 articles reporting NNTs derived from time-to-event outcomes, only 17 applied an appropriate calculation method. Of the 62 articles reporting NNTs, only 21 articles presented corresponding confidence intervals.

Conclusion

The NNT is used as effect measure to present the results from RCTs with binary and time-to-event outcomes in the current medical literature. In the case of time-to-event data incorrect methods were frequently applied. Confidence intervals for NNTs were given in one third of the NNT reporting articles only. In summary, there is much room for improvement in the application of NNTs to present results of RCTs, especially where the outcome is time to an event.

Laypersons' understanding of relative risk reductions: randomised cross-sectional study

Background

Despite increasing recognition of the importance of involving patients in decisions on preventive healthcare interventions, little is known about how well patients understand and utilise information provided on the relative benefits from these interventions. The aim of this study was to explore whether lay people can discriminate between preventive interventions when effectiveness is presented in terms of relative risk reduction (RRR), and whether such discrimination is influenced by presentation of baseline risk.

Methods

The study was a randomised cross-sectional interview survey of a representative sample (n = 1,519) of lay people with mean age 59 (range 40–98) years in Denmark. In addition to demographic information, respondents were asked to consider a hypothetical drug treatment to prevent heart attack. Its effectiveness was randomly presented as RRR of 10, 20, 30, 40, 50 or 60 percent, and half of the respondents were presented with quantitative information on the baseline risk of heart attack. The respondents had also been asked whether they were diagnosed with hypercholesterolemia or had experienced a heart attack.

Results

In total, 873 (58%) of the respondents consented to the hypothetical treatment. While 49% accepted the treatment when RRR = 10%, the acceptance rate was 58–60% for RRR>10. There was no significant difference in acceptance rates across respondents irrespective of whether they had been presented with quantitative information on baseline risk or not.

Conclusion

In this study, lay people's decisions about therapy were only slightly influenced by the magnitude of the effect when it was presented in terms of RRR. The results may indicate that lay people have difficulties in discriminating between levels of effectiveness when they are presented in terms of RRR.

Communicating effectiveness of intervention for chronic diseases: what single format can replace comprehensive information?

Background

There is uncertainty about how GPs should convey information about treatment effectiveness to their patients in the context of cardiovascular disease. Hence we study the concordance of decisions based on one of four single information formats for treatment effectiveness with subsequent decisions based on all four formats combined with a pictorial representation.

Methods

A randomized study comprising 1,169 subjects aged 40–59 in Odense, Denmark. Subjects were randomized to receive information in terms of absolute risk reduction (ARR), relative risk reduction (RRR), number needed to treat (NNT), or prolongation of life (POL) without heart attack, and were asked whether they would consent to treatment. Subsequently the same information was conveyed with all four formats jointly accompanied by a pictorial presentation of treatment effectiveness. Again, subjects should consider consent to treatment.

Results

After being informed about all four formats, 52%–79% of the respondents consented to treatment, depending on level of effectiveness and initial information format. Overall, ARR gave highest concordance, 94% (95% confidence interval (91%; 97%)) between initial and final decision, but ARR was not statistically superior to the other formats.

Conclusion

Decisions based on ARR had the best concordance with decisions based on all four formats and pictorial representation, but the difference in concordance between the four formats was small, and it is unclear whether respondents fully understood the information they received.

Critiques of the risk concept--valid or not?

The increasing use of the risk concept in healthcare has caused concern among medical doctors, especially general practitioners (GPs). Critics have claimed that risk identification and intervention create unfounded anxiety, that the concept of risk is not useful at the individual patient level, that patients' risk concept is different from an epidemiological one, that resources are better spent elsewhere, or that commercial interests take advantage of risk information to promote sales. In this paper the authors discuss the concept of risk and address the critique. There is evidence that commercial interests promote risk interventions, that patients may misunderstand risk information, and that risk information can cause unnecessary anxiety. The authors have found no empirical data on the amount of time primary healthcare providers spend on risk interventions, and have not identified any valid arguments that risk information is not useful for the individual patient. Decision-making under uncertainty is a core element of medical practice, and GPs need to be suitably trained to inform patients such that they make good decisions when they are faced with uncertainty. The concept of risk is therefore useful for GPs, and in fact a key issue. It is concluded that risk critique should be based on sound theory and empirical data. Critics may do well in making clear distinctions between facts and value judgements.

Can postponement of an adverse outcome be used to present risk reductions to a lay audience? A population survey

BACKGROUND

For shared decision making doctors need to communicate the effectiveness of therapies such that patients can understand it and discriminate between small and large effects. Previous research indicates that patients have difficulties in understanding risk measures. This study aimed to test the hypothesis that lay people may be able to discriminate between therapies when their effectiveness is expressed in terms of postponement of an adverse disease event.

METHODS

In 2004 a random sample of 1,367 non-institutionalized Danes aged 40+ was interviewed in person. The participants were asked for demographic information and asked to consider a hypothetical preventive drug treatment. The respondents were randomized to the magnitude of treatment effectiveness (heart attack postponement of 1 month, 6 months, 12 months, 2 years, 4 years and 8 years) and subsequently asked whether they would take such a therapy. They were also asked whether they had hypercholesterolemia or had experienced a heart attack.

RESULTS

In total 58% of the respondents consented to the hypothetical treatment. The proportions accepting treatment were 39%, 52%, 56%, 64%, 67% and 73% when postponement was 1 month, 6 months, 12 months, 2 years, 4 years and 8 years respectively. Participants who thought that the effectiveness information was difficult to understand, were less likely to consent to therapy (p = 0.004).

CONCLUSION

Lay people can discriminate between levels of treatment effectiveness when they are presented in terms of postponement of an adverse event. The results indicate that such postponement is a comprehensible measure of effectiveness.

Expressing medicine side effects: assessing the effectiveness of absolute risk, relative risk, and number needed to harm, and the provision of baseline risk information

OBJECTIVE

To assess the effectiveness of absolute risk, relative risk, and number needed to harm formats for medicine side effects, with and without the provision of baseline risk information.

METHODS

A two factor, risk increase format (relative, absolute and NNH)xbaseline (present/absent) between participants design was used. A sample of 268 women was given a scenario about increase in side effect risk with third generation oral contraceptives, and were required to answer written questions to assess their understanding, satisfaction, and likelihood of continuing to take the drug.

RESULTS

Provision of baseline information significantly improved risk estimates and increased satisfaction, although the estimates were still considerably higher than the actual risk. No differences between presentation formats were observed when baseline information was presented. Without baseline information, absolute risk led to the most accurate performance.

CONCLUSION

The findings support the importance of informing people about baseline level of risk when describing risk increases. In contrast, they offer no support for using number needed to harm.

PRACTICE IMPLICATIONS

Health professionals should provide baseline risk information when presenting information about risk increases or decreases. More research is needed before numbers needed to harm (or treat) should be given to members of the general populations.