The process of “mapping” onto generic preference-based outcome measures is increasingly being used as a means of generating health utilities for application within health economic evaluations (Reference Brazier, Yang and Tsuchiya1). Mapping involves the development and use of an algorithm (or algorithms) to predict the primary outputs of generic preference-based outcome measures, i.e., health utility values, using data on other indicators or measures of health. The source predictive measure may be a non–preference-based indicator or measure of health outcome or, more exceptionally, a preference-based outcome measure that is not preferred by the local health technology assessment agency. The algorithm(s) can subsequently be applied to data from clinical trials, observational studies, or economic models containing the source predictive measure(s) to predict health utility values in contexts where the target generic preference-based measure is absent. The predicted health utility values can then be analyzed using standard methods for individual-level data (e.g., within a trial-based economic evaluation), or summarized for each health state within a decision-analytic model.
Over recent years, there has been a rapid increase in the publication of studies that use mapping techniques to predict health utility values, and databases of published studies in this field are beginning to emerge (Reference Dakin2). Some authors (Reference Chuang and Whitehead3) and agencies (Reference Longworth and Rowen4) concerned with technology appraisals have issued technical guides for the conduct of mapping research. However, guidance for the reporting of mapping studies is currently lacking. In keeping with health-related research more broadly (Reference Moher, Schulz and Simera5), mapping studies should be reported fully and transparently to allow readers to assess the relative merits of the investigation (Reference Moher, Simera and Schulz6). Moreover, there may be significant opportunity costs associated with regulatory and reimbursement decisions for new technologies informed by misleading findings from mapping studies. This has led to the development of the MAPS (MApping onto Preference-based measures reporting Standards) reporting statement, which we summarize in this study.
The aim of the MAPS reporting statement is to provide recommendations, in the form of a checklist of essential items, which authors should consider when reporting a mapping study. It is anticipated that the checklist will promote complete and transparent reporting by researchers. The focus, therefore, is on promoting the quality of reporting of mapping studies, rather than the quality of their conduct, although it is possible that the reporting statement will also indirectly enhance the methodological rigor of the research (Reference Narahari, Ryan and Aggithaya7). The MAPS reporting statement is primarily targeted at researchers developing mapping algorithms, the funders of the research, and peer reviewers and editors involved in the manuscript review process for mapping studies (Reference Narahari, Ryan and Aggithaya5;Reference Moher, Simera and Schulz6). In developing the reporting statement, the term “mapping” is used to cover all approaches that predict the outputs of generic preference-based outcome measures using data on other indicators or measures of health, and encompasses related forms of nomenclature used by some researchers, such as “cross-walking” or “transfer to utility” (Reference Brazier, Yang and Tsuchiya1;Reference Mortimer, Segal and Sturm8). Similarly, the term “algorithm” is used in its broadest sense to encompass statistical associations and more complex series of operations.
DEVELOPMENT OF THE MAPS STATEMENT
The development of the MAPS reporting statement was informed by recently published guidance for health research reporting guidelines (Reference Moher, Schulz and Simera5) and broadly modeled other recent reporting guideline developments (Reference Bossuyt, Reitsma and Bruns9–Reference Husereau, Drummond and Petrou14). A working group comprised of six health economists (S.P., O.R.A., H.D., L.L., M.O., A.G.) and one Delphi methodologist (R.F.) was formed following a request from an academic journal to develop a reporting statement for mapping studies. One of the working group members (H.D.) had previously conducted a systematic review of studies mapping from clinical or health-related quality of life measures onto the EQ-5D (Reference Dakin2). Using the search terms from this systematic review, as well as other relevant articles and reports already in our possession, a broad search for reporting guidelines for mapping studies was conducted. This confirmed that no previous reporting guidance had been published. The working group members, therefore, developed a preliminary de novo list of twenty-nine reporting items and accompanying explanations. Following further review by the working group members, this was subsequently distilled into a list of twenty-five reporting items and accompanying explanations.
Members of the working group identified sixty-two possible candidates for a Delphi panel from a pool of active researchers and stakeholders in this field. The candidates included individuals from academic and consultancy settings with considerable experience in mapping research, representatives from health technology assessment agencies that routinely appraise evidence informed by mapping studies, and biomedical journal editors. Health economists from the MAPS working group were included in the Delphi panel. A total of forty-eight of the sixty-two (77.4 percent) individuals agreed to participate in a Delphi survey aimed at developing a minimum set of standard reporting requirements for mapping studies with an accompanying reporting checklist.
The Delphi panelists were sent a personalized link to a Web-based survey, which had been piloted by members of the working group. Nonresponders were sent up to two reminders after 14 and 21 days. The panelists were anonymous to each other throughout the study and their identities were known only to one member of the working group. The panelists were invited to rate the importance of each of the twenty-five candidate reporting items identified by the working group on a 9-point rating scale (1, “not important”, to 9, “extremely important”); describe their confidence in their ratings (“not confident,” “somewhat confident,” or “very confident”); comment on the candidate items and their explanations; suggest additional items for consideration by the panelists in subsequent rounds; and to provide any other general comments. The candidate reporting items were ordered within six sections: (i) title and abstract, (ii) introduction, (iii) methods, (iv) results, (v) discussion, and (vi) other. The panelists also provided information about their geographical area of work, gender, and primary and additional work environments. The data were imported into Stata (version 13; Stata-Corp, College Station, TX) for analysis.
A modified version of the Research ANd Development (RAND)/University of California Los Angeles (UCLA) appropriateness method was used to analyze the round one responses (Reference Fitch, Bernstein and Aguilar15). This involved calculating the median score, the inter-percentile range (IPR) (30th and 70th), and the inter-percentile range adjusted for symmetry (IPRAS), for each item ( i ) being rated. The IPRAS includes a correction factor for asymmetric ratings, and panel disagreement was judged to be present in cases if IPR i >IPRAS i (Reference Fitch, Bernstein and Aguilar15). We modified the RAND/UCLA approach by asking panelists about “importance” rather than “appropriateness” per se. Assessment of importance followed the classic RAND/UCLA definitions, categorized simply as whether the median rating fell between 1 and 3 (unimportant), 4 and 6 (neither unimportant nor important), or 7 and 9 (important) (Reference Fitch, Bernstein and Aguilar15).
The results of round one of the Delphi survey were reviewed at a face-to-face meeting of the working group. A total of forty-six of the forty-eight (95.8 percent) individuals who agreed to participate completed round one of the survey. Of the twenty-five items, twenty-four were rated as important, with one item (“Source of Funding”) rated as neither unimportant nor important. There was no evidence of disagreement on ratings of any items according to the RAND/UCLA method. These findings did not change when the responses of the MAPS working group were excluded. Based on the qualitative feedback received in round one, items describing “Modelling Approaches” and “Repeated Measurements” were merged, as were items describing “Model Diagnostics” and “Model Plausibility.” In addition, amendments to the wording of several recommendations and their explanations were made in the light of qualitative feedback from the panelists.
Panelists participating in round one were invited to participate in a second round of the Delphi survey. A summary of revisions made following round one was provided. This included a document in which revisions to each of the recommendations and explanations were displayed in the form of track changes. Panelists participating in round two were provided with group outputs (mean scores and their standard deviations, median scores and their IPRs, histograms and RAND/UCLA labels of importance and agreement level) summarizing the round one results (and disaggregated outputs for the merged items). They were also able to view their own round one scores for each item (and disaggregated scores for the merged items). Panelists participating in round two were offered the opportunity to revise their rating of the importance of each of the items and informed that their rating from round one would otherwise hold. For the merged items, new ratings were solicited. Panelists participating in round two were also offered the opportunity to provide any further comments on each item or any further information that might be helpful to the group. Nonresponders to the second round of the Delphi survey were sent up to two reminders after 14 and 21 days. The analytical methods for the round two data mirrored those for the first round.
The results of the second round of the Delphi survey were reviewed at a face-to-face meeting of the working group. A total of thirty-nine of the forty-six (84.8 percent) panelists participating in round one completed round two of the survey. All twenty-three items included in the second round were rated as important with no evidence of disagreement on ratings of any items according to the RAND/UCLA method. Qualitative feedback from the panelists participating in round two led to minor modifications to wording of a small number of recommendations and their explanations. This was fed back to the round two respondents who were given a final opportunity to comment on the readability of the final set of recommendations and explanations. Based on these methods, a final consensus list of twenty-three reporting items was developed.
THE MAPS STATEMENT
The MAPS statement is a twenty-three item checklist of recommendations (Table 1) that we consider essential for complete and transparent reporting of studies that map onto generic preference-based outcome measures. The twenty-three reporting items are presented numerically and categorized within six sections, namely: (i) title and abstract (two items). (ii) introduction (two items). (iii) methods (nine items). (iv) results (six items). (v) discussion (three items). and (vi) other (one item). The reporting of each item does not necessarily have to follow the order within the MAPS statement. Rather, what is important is that each recommendation is addressed either in the main body of the report or its appendices. Several biomedical journals have endorsed the MAPS statement. These include Applied Health Economics and Health Policy, Health and Quality of Life Outcomes, International Journal of Technology Assessment in Health Care, Journal of Medical Economics, Medical Decision Making, PharmacoEconomics, and Quality of Life Research. We encourage other journals and research interest groups to endorse the MAPS statement and authors to adhere to its principles.
Table 1. Checklist of Items to Include When Reporting a Mapping Study
MAPS EXPLANATION AND ELABORATION PAPER
In addition to the MAPS reporting statement, we have produced a supporting Explanation and Elaboration paper (Reference Petrou, Dakin, Longworth, Oppe, Froud and Gray16), modeled on those developed for other reporting guidelines (Reference Bossuyt, Reitsma and Bruns9–Reference Husereau, Drummond and Petrou14). The reporting items contained within the MAPS statement are best understood by referring to the information contained within this accompanying document. The Explanation and Elaboration paper provides exemplars of good reporting practice identified from the published literature for each reporting item. In addition, it provides a detailed explanation to accompany each recommendation, supported by a rationale and relevant evidence where available. The development of the Explanation and Elaboration paper was completed following several iterations produced by members of the working group, after which the examples and explanations were shared with the Delphi panelists for final revisions to improve readability and their approval. The Explanation and Elaboration paper also summarizes the characteristics of the Delphi panelists and provides detailed statistics for item ratings at each Delphi round.
DISCUSSION
Over recent years, there has been a rapid increase in the publication of studies that use mapping techniques to predict health utility values. One recent review article identified ninety studies published up to the year 2013 reporting 121 mapping algorithms between clinical or health-related quality of life measures and the EQ-5D (Reference Dakin2). That review article excluded mapping algorithms targeted at other generic preference-based outcome measures that can generate health utilities, such as the SF-6D (Reference Brazier, Roberts and Deverill17) and the Health Utilities Index (HUI) (Reference Feeny, Furlong and Boyle18), which have been the target of numerous other mapping algorithms (e.g., 1;19–24). Moreover, the popularity of the mapping approach for estimating health utilities is unlikely to wane, given the numerous contexts within health economic evaluation where primary data collection is challenging. However, mapping introduces additional uncertainty and collection of primary data with the preferred utility instrument is preferable.
The MAPS reporting statement was developed to provide recommendations, in the form of a checklist of essential items, which authors should consider when reporting mapping studies. Guidance for the reporting of mapping studies was not previously available in the literature. The overall aim of MAPS is to promote clarity, transparency, and completeness of reporting of mapping studies. It is not intended to act as a methodological guide, nor as a tool for assessing the quality of study methodology. Rather, it aims to avoid misleading conclusions being drawn by readers, and ultimately policy makers, as a result of sub-optimal reporting. In keeping with other recent health research reporting guidelines, we have also produced an accompanying Explanation and Elaboration paper (Reference Petrou, Dakin, Longworth, Oppe, Froud and Gray16) to facilitate a deeper understanding of the twenty-three items contained within the MAPS reporting statement. That paper should hopefully act as a pedagogical framework for researchers reporting mapping studies.
The development of the MAPS reporting statement, and its Explanation and Elaboration document, was framed by recently published guidance for health research reporting guidelines (Reference Moher, Schulz and Simera5). The Delphi panel was composed of a multi-disciplinary, multi-national team of content experts and journal editors. The panel members included people experienced in conducting mapping studies; of the eighty-four researchers who were first authors on papers included in a recent review of EQ-5D mapping studies (Reference Dakin2), thirty-one (36.9 percent) were included as panelists. We have no evidence to believe that a larger panel would have altered the final set of recommendations. The Delphi methodologies that we applied included analytical approaches only recently adopted by developers of health reporting guidelines (Reference Fitch, Bernstein and Aguilar15). We are unable to assess whether a strict adherence to the MAPS checklist will increase the word counts of mapping reports. It is our view that the increasing use of online appendices by journals should permit comprehensive reporting even in the context of strict word limits for the main body of reports.
Evidence for other health research reporting guidelines suggests that reporting quality improved after the introduction of reporting checklists (Reference Moher, Jones and Lepage25–Reference Plint, Moher and Morrison27), although there is currently no empirical evidence that adoption of MAPS will improve the quality of reporting of mapping research. Future research planned by the MAPS working group will include a before and after evaluation of the benefits (and indeed possible adverse effects) of the introduction of the MAPS reporting statement. It will also be necessary to update the MAPS reporting statement in the future to address conceptual, methodological, and practical advances in the field. Potential methodological advances that might be reflected in an update might include shifts toward more complex model specifications, better methods for dealing with uncertainty, and guidance on appropriate use of measures of prediction accuracy, such as mean absolute error (MAE) and mean square error (MSE). The MAPS working group plans to assess the need for an update of the reporting checklist in 5 years’ time.
In conclusion, this study summarizes a new reporting statement developed for studies that map onto generic preference-based outcome measures. We encourage health economic and quality of life journals to endorse MAPS, promote its use in peer review and update their editorial requirements and “Instructions to Authors” accordingly.
ACKNOWLEDGMENTS
This article is a joint publication by Applied Health Economics and Health Policy, Health and Quality of Life Outcomes, International Journal of Technology Assessment in Health Care, Journal of Medical Economics, Medical Decision Making, Pharmacoeconomics, and Quality of Life Research. Funding: No external funding was received for this study. All members of the working group acted on a voluntary basis.
We are grateful to the following individuals, who consented to being acknowledged publicly, for their comments and participation in the Delphi Panel: Roisin Adams, Roberta Ara, Nick Bansback, Garry Barton, Andy Briggs, Chris Carswell, Gang Chen, Doug Coyle, Ralph Crott, Richard Edlin, Alastair Fischer, Juan Manuel Ramos-Goñi, Ola Ghatnekar, Patrick Gillard, Ning Yan Gu, Annie Hawton, Haomiao Jia, Kamran Khan, Billingsley Kaambwa, Nick Kontodimopoulos, Quang Le, Jason Madan, Katherine MacGilchrist, David Meads, Duncan Mortimer, Bhash Naidoo, Angus Ng, Nalin Payakachat, Simon Pickard, Rafael Pinedo-Villanueva, Eleanor Pullenayegum, Jeff Richardson, Janet Robertson, Jeff Round, Donna Rowen, Sean Rundell, Paulos Teckle, Matthijs Versteegh, Feng Xie, and Tracey Young.
CONFLICTS OF INTEREST
R.F. is a shareholder and a director of a company (Clinvivo Limited) that provides services for Delphi studies. However, these services were not used in this study and thus notwithstanding the connection, R.F. declares that he has no conflicts of interest. The remaining authors (S.P., O.R.A., H.D., L.L., M.O., A.G.) have no conflicts of interest to declare. All authors contributed to the study design and conduct, interpretation of results and report writing. S.P. acts as the guarantor.
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