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Micro-costing in health and medicine: a critical appraisal Xiao Xu1, Christina M. Lazar2 and Jennifer Prah Ruger3*

Abstract

Background: Concerns about rising health care costs require rigorous economic study to inform clinical and policy decision-making. Micro-costing is a cost estimation methodology employing detailed resource utilization and unit cost data to generate precise estimates of economic costs. Micro-costing studies have not been critically appraised.

Methods: Critical appraisal of micro-costing studies in English. Studies fully or predominantly employing micro- costing were appraised for methodological and reporting quality through economic evaluation guidelines (Evers, Drummond, Consolidated Health Economic Evaluation Reporting Standards (CHEERS), Fukuda and Imanaka checklists). Following the Panel on Cost Effectiveness in Health and Medicine, micro-costing studies were defined as involving “direct enumeration and costing out of every input consumed in the treatment of a particular patient.”

Results: Full or predominant micro-costing studies included neoplasms (18.5%), infectious and parasitic diseases (17.9%), and diseases of circulatory systems (10.8%) as the most studied diseases. 36.9% were in the United States and 34.9% were in Europe. 33.8% did not report analytic perspective, 32.8% did not report price year, 3.6% did not inflation adjust cost data, and 44.1% did not specify inflation adjustment. 86.2% did not separately report unit costs and resource utilization quantity, 14.9 and 19.5% did not provide sufficient detail to assess appropriateness of measured physical units or valued costs.

Conclusions: Micro-costing studies vary widely in methodological and reporting quality, highlighting the need to standardize methods and reporting of micro-costing studies and develop tools for their evaluation.

Keywords: Micro-costing, Economic evaluation, Resource allocation, Health and medicine

Key messages (1) Micro-costing studies vary widely in methodological and reporting quality; (2) There is a need to standardize methods and reporting of micro-costing studies and de- velop tools for their evaluation.

Introduction Concerns about rising health care costs require rigorous economic study to inform clinical and policy decision-

making. Advances in medical knowledge and technology results in rapid diffusion of new health interventions that cannot be precisely costed by existing estimates or prices. Micro-costing is particularly relevant for estimat- ing costs of new interventions, but existing interven- tions, too, benefit from this methodology. By measuring detailed resource utilization and unit costs, micro- costing methodology generates precise cost estimates and has been considered the preferred method for esti- mating costs of health interventions [1]. The conduct, appraisal and reporting of micro-costing

studies can be complex due to the detailed cost categorization and data collection involved. Existing guidelines for economic evaluations, the Drummond checklist [2], Evers checklist [3], and Consolidated

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* Correspondence: [email protected] 3Department of Medical Ethics and Health Policy, Perelman School of Medicine, The Leonard Davis Institute of Health Economics, School of Social Policy & Practice, University of Pennsylvania, 3701 Locust Walk, Philadelphia, PA 19104, USA Full list of author information is available at the end of the article

Xu et al. Health Economics Review (2021) 11:1 https://doi.org/10.1186/s13561-020-00298-5

Health Economic Evaluation Reporting Standards (CHEERS) checklist [4], have focused on full economic evaluations. Although these guidelines have been instru- mental in enhancing the quality, transparency, and com- parability of economic evaluation studies, they do not provide sufficient guidelines regarding appropriate tech- niques and standards to use in micro-costing studies. Moreover, while the recently convened Second Panel on Cost-Effectiveness in Health and Medicine [5, 6] up- dated recommendations concerning the conduct of eco- nomic evaluations, there remains no standardized requirement about how to conduct, appraise, or report micro-costing studies [7]. Given this gap in the literature, current practices in

conducting and reporting micro-costing studies likely vary substantially. This may hinder comparison of re- search findings across studies and interpretation of study results. The objective of this study was to critically ap- praise micro-costing studies to assess their methodo- logical and reporting quality and the appropriateness of existing economic evaluation guidelines for this purpose.

Methods A critical appraisal of micro-costing studies in English was conducted. Ovid MEDLINE, EconLit, BIOSIS Pre- views, Embase, Scopus, and National Health Service Eco- nomic Evaluation Database were searched for records through July 2015. Following Gold and colleagues [1], micro-costing studies were defined as those that in- volved “direct enumeration and costing out of every in- put consumed in the treatment of a particular patient”. To inform future design and reporting of micro-costing studies, analysis was limited to studies that fully or pre- dominantly used micro-costing in their cost estimation and studies that only partially or minimally involved micro-costing were excluded. To inform future research, the focus was on research studies with a defined patient sample and research question, studies with a primary goal to inform hospital financial management or esti- mate unit cost per medical service were excluded. A detailed data collection form was developed to ex-

tract comprehensive data on study design and reporting characteristics for each micro-costing study. Data col- lected included study population, study intervention, analytical perspective, type of economic evaluation, eco- nomic and health outcomes evaluated, time horizon of analysis, discounting, price and currency, method of data collection for quantity and unit cost information, cost components included, and use of sensitivity analysis. These data elements captured sufficient specifics to fa- cilitate a detailed characterization of studies. To evaluate study quality, validated economic evalu-

ation checklists were employed, including the Drum- mond checklist [2] and Evers checklist [3]. The

Drummond checklist contained 35 items evaluating the quality of an economic evaluation regarding its study de- sign, data collection, analysis, and interpretation of re- sults [2]. The Evers checklist included 19 items covering a core set of methodological standards for economic evaluations [3]. For each checklist, the percentage of ap- plicable items that a study scored “Yes” was calculated. Since not all checklist items were applicable to a given study, inapplicable items were excluded when calculating the percentage of Drummond checklist and Evers check- list items that the study scored “Yes”. Higher percentage indicates better quality. A single item classification scheme developed by

Fukuda and Imanaka [8] was employed to further evalu- ate reporting quality. This scheme categorized each study into four levels based on transparency of their reporting: “All components of costs were described and data for both quantity and unit price of resources were reported for each component”, “All components of costs were described and data for costs in each component were reported”, “All components of costs were described but data for costs in each component were not re- ported”, and “Only scope of costing was described but components of costs were not described” [8]. Two researchers independently screened studies and

performed data extraction. Disagreements were discussed and resolved by consensus as well as consultation with a third researcher. Descriptive statistics (e.g., frequency and percentages) were used to summarize key study design and reporting characteristics. SAS version 9.4 was used for all data analysis (SAS Institute Inc., Cary, NC).

Results 195 studies were critically appraised. The number of studies that fully or predominantly applied the micro- costing methodology increased over time. General char- acteristics of the 195 micro-costing studies are summa- rized in Table 1. Neoplasms, infectious and parasitic diseases, and diseases of the circulatory systems were the most commonly studied disease areas, accounting for 18.5, 17.9, and 10.8% of the studies, respectively. In terms of geographic location, 36.9% were conducted in the United States, and 34.9% were performed in Euro- pean countries. Most were observational studies (67.2%), while 32.8% were based on randomized controlled trials. When categorized by type of economic evaluation, a small proportion were full economic evaluations, includ- ing 24.1% cost-effectiveness analyses, 5.6% cost-utility analyses, 1.5% cost-benefit analyses, and 5.6% cost- minimization analyses. In contrast, 19.0% compared costs between two or more interventions without evalu- ating effectiveness and 23.1% estimated costs for a par- ticular intervention without a comparison group or evaluating effectiveness.

Xu et al. Health Economics Review (2021) 11:1 Page 2 of 8

Table 1 General characteristics of micro-costing studies

Characteristics N (%)

Distribution of disease area (based on ICD-9-CM diagnosis chapters)a

Neoplasms 36 (18.5%)

Infectious and parasitic diseases 35 (17.9%)

Diseases of the circulatory system 21 (10.8%)

Mental disorders 19 (9.7%)

Diseases of the digestive system 15 (7.7%)

Endocrine, nutritional and metabolic diseases, and immunity disorders 14 (7.2%)

Diseases of the nervous system and sense organs 7 (3.6%)

Diseases of the musculoskeletal system and connective tissue 6 (3.1%)

Diseases of the skin and subcutaneous tissue 5 (2.6%)

Injury and poisoning 5 (2.6%)

Diseases of the genitourinary system 4 (2.1%)

Congenital anomalies 4 (2.1%)

Symptoms, signs, and ill-defined conditions 4 (2.1%)

Supplementary classification of factors influencing health status and contact with health services 4 (2.1%)

Non-groupable disease/condition 3 (1.5%)

Diseases of the respiratory system 1 (0.5%)

Complications of pregnancy, childbirth, and puerperium 1 (0.5%)

Supplementary classification of external causes of injury and poisoning 1 (0.5%)

No specific disease/condition 23 (11.8%)

Distribution of study geographic locationa

USA 72 (36.9%)

Europe 68 (34.9%)

Asia 23 (11.8%)

Africa 19 (9.7%)

Australia/New Zealand/Micronesia 6 (3.1%)

Canada 6 (3.1%)

Latin America/Caribbean (including Mexico) 2 (1.0%)

Type of study designa

Observational study 131 (67.2%)

Randomized controlled trial 64 (32.8%)

Decision analytic modeling 4 (2.1%)

Other economic modeling 2 (1.0%)

Other study design 2 (1.0%)

Type of economic evaluationa

Cost effectiveness analysis 47 (24.1%)

Cost utility analysis 11 (5.6%)

Cost minimization analysis 11 (5.6%)

Cost benefit analysis 3 (1.5%)

Cost consequence analysis 12 (6.2%)

Cost comparison analysis (without evaluation of effectiveness) 37 (19.0%)

Single intervention cost analysis (without evaluation of effectiveness) 45 (23.1%)

Single intervention cost analysis (with evaluation of effectiveness) 16 (8.2%)

Cost of illness analysis 21 (10.8%)

Xu et al. Health Economics Review (2021) 11:1 Page 3 of 8

Key design features were poorly reported (Table 1). Approximately one third of studies did not specify per- spective, and only 20.5% adopted a societal perspective. 32.8% of studies did not specify price year, while 44.1% did not state whether costs from different years were

inflation adjusted. 3.6% did not perform inflation adjust- ment when cost data were collected across multiple cal- endar years and did not provide justification. 48.2% of studies did not perform any sensitivity analysis to ac- count for uncertainty in cost estimation. A large

Table 1 General characteristics of micro-costing studies (Continued)

Characteristics N (%)

Other economic evaluation 1 (0.5%)

Economic evaluation perspective specified

Yes 129 (66.2%)

No 66 (33.8%)

Actual economic evaluation perspective useda

Hospital/clinic/provider 111 (56.9%)

Societal 40 (20.5%)

Health care program 21 (10.8%)

Health care system 17 (8.7%)

Insurer 9 (4.6%)

Employer 2 (1.0%)

Other 15 (7.7%)

Price year specified

Yes 131 (67.2%)

No 64 (32.8%)

Currency specified

Yes 194 (99.5%)

No 1 (0.5%)

Inflation adjustment

Yes 83 (42.6%)

No 7 (3.6%)

Not specified 86 (44.1%)

Not applicable 19 (9.7%)

Sensitivity analysisa

Deterministic sensitivity analysis 90 (46.2%)

Stochastic (probabilistic) sensitivity analysis 13 (6.7%)

Other sensitivity analysis 6 (3.1%)

No sensitivity analysis 94 (48.2%)

Funding supporta

Government funding source 79 (40.5%)

Non-profit non-government funding source 47 (24.1%)

Industry sponsored study 28 (14.4%)

No funding 15 (7.7%)

Not specified 55 (28.2%)

Conflict of interest

Yes 12 (6.2%)

No 76 (39.0%)

Not specified 107 (54.9%)

Percentages may not add to 100 due to rounding a A study may fall into more than one of the listed categories

Xu et al. Health Economics Review (2021) 11:1 Page 4 of 8

proportion of micro-costing studies did not report na- ture of funding (28.2%) or conflict of interest (54.9%). Study characteristics related to cost measurement are

summarized in Table 2. 49.7% referred to their own methodology as micro-costing. When assessed by the Fukuda and Imanaka [8] transparency scale, 13.8% of studies described all cost components and reported both quantity and unit cost of resources for each component, whereas 80.5% described cost components and reported data for cost in each component but did not separately report quantity and unit cost of all resources used. In terms of specific cost components estimated, virtually all studies (95.4%) included personnel costs, 88.2% included material, supplies and consumables, and 68.2% included overhead costs. Provider/staff interview, hospital admin- istrative or cost/accounting databases, and time-motion study were the most common methods of collecting data on quantity of resource utilization, used by 36.4, 29.2 and 21.5% of studies, respectively. Invoice price, hospital administrative or cost/accounting database, and fee schedules were most commonly used to obtain unit cost data, accounting for 31.8, 30.8, and 24.1% of studies, respectively. Evaluation based on the Drummond checklist [2] and

Evers checklist [3] showed moderate quality of these studies. Among the checklist items applicable to each study, the average proportion of items that scored “Yes” was 72.5% on Drummond checklist and 69.6% on Evers checklist. 72.8% did not specify analytical perspective or did not use a societal perspective and did so without justification, 83.6% did not explain why costs and bene- fits were not discounted, and 68.7% did not perform suf- ficient sensitivity analysis on important variables. While most studies measured physical units and unit costs ap- propriately, 14.9 and 19.5% did not provide sufficient de- tail to inform whether they appropriately measured physical units or valued costs, respectively. Four studies compared the impact of micro-costing

versus other costing methods, such as gross-costing, on cost estimation [9–12]. Their findings showed that, de- pending on services type, use of different costing methods could result in large differences in cost esti- mates and may affect decision-making regarding the cost-effectiveness of alternative interventions [9, 11, 12]. The micro-costing method was considered more trans- parent [9] and provided more detailed information to help identify cost drivers [11]. In addition, three studies compared bottom-up (i.e., assessed resource utilization for each cost item and then aggregated for a total sys- tem) and top-down (i.e., assessed resource utilization for a total system and then allocated to individual cost items) [13] costing. They demonstrated that bottom-up costing generated more accurate estimates for labor in- tensive services [12, 14, 15].

Discussion This critical appraisal of micro-costing studies in health and medicine suggests that use of micro-costing methods, while increasing, has largely varied in the qual- ity of conducting and reporting of micro-costing ana- lyses. Studies often did not adequately address key design issues and lacked sufficient detail or transparency in explaining study design. The few studies available that compared micro-costing with other costing methods suggest that micro-costing is the preferred method for generating accurate cost estimates, especially for studies that involve services that are labor intensive. These findings highlight the importance and need for

rigorous guidelines to help standardize the conduct and reporting of micro-costing studies. Future efforts to de- velop a checklist specifically tailored to micro-costing studies [7] will be instrumental. Prior checklists have evaluated full economic evaluations such as cost- effectiveness analysis and many of the checklist ques- tions are not applicable to micro-costing studies. More- over, many specific aspects of micro-costing studies – such as detailed enumeration of resource utilization quantity and unit costs – are not fully assessed by exist- ing checklists. Closer attention to the design and report- ing of micro-costing studies is needed from the research community, and quality standards deserve consideration by relevant professional organizations, such as future Panels on Cost-Effectiveness in Health and Medicine, the International Society for Pharmacoeconomics and Outcomes Research, and the Society for Medical Deci- sion Making. Our study identified several limitations in current micro-costing studies, which may assist future efforts. Lack of sufficient detail about measurement of resource utilization quantity and unit costs requires par- ticular attention in development of quality standards or checklists for micro-costing studies. Variability existed in how studies have referred to their

micro-costing method. Some studies stated bottom-up approach or did not name their method, while other studies used different terminologies such as ingredient based approach. Micro-costing methods need to be more systematically reported and consistently referred to when applied. This can further improve comparability and transparency of future studies. This study has several limitations. First, our selection

of micro-costing studies focused on those that involved systematic collection of quantity and unit costs data for a defined patient cohort. Other researchers may have used broader definitions for micro-costing and may in- clude other types of studies such as those focusing on hospital accounting or financial interest or estimating unit costs of a particular procedure or laboratory test without a defined patient sample. Second, studies that only cited use of hospital accounting databases without

Xu et al. Health Economics Review (2021) 11:1 Page 5 of 8

Table 2 Micro-costing related characteristics of studies

Characteristics N (%)

Whether referred to its own methodology as micro-costing

Yes 97 (49.7%)

No 98 (50.3%)

Separate reporting of quantity and unit cost data

Yes 27 (13.8%)

No 168 (86.2%)

Classification of transparency of cost estimates [8]

All components of costs were described and data for both quantity and unit cost of resources were reported for each component 27 (13.8%)

All components of costs were described and data for costs in each component were reported 157 (80.5%)

All components of costs were described but data for costs in each component were not reported 9 (4.6%)

Only scope of costing was described but components of costs were not Described 2 (1.0%)

Cost components includeda

Personnel 186 (95.4%)

Materials/supplies/consumables 172 (88.2%)

Overhead 133 (68.2%)

Equipment/device 118 (60.5%)

Facility 112 (57.4%)

Medication 95 (48.7%)

Transportation 74 (37.9%)

Laboratory/diagnostic/imaging test 68 (34.9%)

Productivity loss 37 (19.0%)

Food 28 (14.4%)

Furniture 22 (11.3%)

Child/elderly care 2 (1.0%)

Other 60 (30.8%)

Method of quantity data collectiona

Provider/staff interview 71 (36.4%)

Hospital administrative cost/accounting database 57 (29.2%)

Time-motion study 42 (21.5%)

Medical chart/record review 30 (15.4%)

Patient self-report 25 (12.8%)

Synthesis of literature 6 (3.1%)

Clinical guideline 3 (1.5%)

Other 112 (57.4%)

Not clear 32 (16.4%)

Method of unit cost data collectiona

Invoice price 62 (31.8%)

Hospital administrative cost/accounting database 60 (30.8%)

National/regional/provincial/hospital/insurer fee schedule 47 (24.1%)

Hospital/clinic/provider price catalogue 8 (4.1%)

Human resources/payroll record 7 (3.6%)

Other 126 (64.6%)

Not clear 37 (19.0%)

Percentages may not add to 100 due to rounding a A study may fall into more than one of the listed categories

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providing sufficient details regarding the collection or tracking of quantity and unit cost data were excluded because lack of such information precluded verifying whether the study used micro-costing methods. As hos- pitals are increasingly adopting micro-costing or activity-based cost allocation systems, researchers may be able to draw on such electronic data to facilitate data collection. However, these studies should provide suffi- cient detail regarding key elements of micro-costing methodology in order to enhance the transparency and usefulness of information. Third, studies that claimed micro-costing but provided little information to verify their costing methodology, were excluded, thus the ap- praisal of included studies may overestimate the quality of existing micro-costing studies. Although micro-costing may not always be practical, it

has unique advantages compared with the more com- monly used gross-costing method. It allows more accur- ate cost estimation, and is particularly useful for evaluating the economic impact of new interventions that lack established cost estimates [16, 17] although existing interventions, too, benefit from this method- ology. Micro-costing should be the preferred method in all areas of health and medicine when such data are available. It is also increasingly a preferred method for policy purposes [18] and a measure of accountability [19]. Given the complexity of micro-costing method- ology and our findings of poor quality in some key as- pects of study design and reporting, more attention and effort are needed to better guide future studies. Develop- ment of a checklist specifically for micro-costing studies will be instrumental to establishing quality standards and promoting comparability and transparency in future research [7]. There is a need especially for standardizing terminology in micro-costing studies.

Conclusion Micro-costing studies vary widely in methodological and reporting quality, highlighting the need to standardize methods and reporting of micro-costing studies and de- velop tools for their evaluation.

Supplementary Information The online version contains supplementary material available at https://doi. org/10.1186/s13561-020-00298-5.

Additional file 1.

Abbreviations CHEERS: Consolidated Health Economic Evaluation Reporting Standards; MEDLINE: Medical Literature Analysis and Retrieval System Online; BIOSIS Previews: Biological Abstracts, Reports, Reviews, and Meetings

Authors’ contributions JPR, XX, CL have made substantial intellectual contributions to all of the following aspects of the work: conception and planning of the work that led

to the manuscript or acquisition, analysis and interpretation of the data, or both; and drafting and/or critical revision of the manuscript for important intellectual content; and authors read and approved the final manuscript. All authors have made substantial intellectual contributions, meet all authorship criteria and take full public responsibility for the content of the work.

Funding This research was supported by a grant from the National Institutes of Health (National Institute on Drug Abuse grant R01DA025555). We acknowledge funding, in part, by the Vice Provost for Research University Research Foundation at the University of Pennsylvania.

Availability of data and materials All data supporting this study is provided in the results section of this paper and as supplementary information accompanying this paper.

Ethics approval and consent to participate No participants in this study, data extraction form was developed to extract data from existing articles.

Consent for publication All authors provide Health Economics Review, Biomed Central, consent for publication.

Competing interests No competing interests to declare.

Author details 1Department of Obstetrics, Gynecology and Reproductive Sciences, Yale School of Medicine, New Haven, USA. 2Department of Psychiatry, VA Connecticut Healthcare System, Yale School of Medicine, New Haven, USA. 3Department of Medical Ethics and Health Policy, Perelman School of Medicine, The Leonard Davis Institute of Health Economics, School of Social Policy & Practice, University of Pennsylvania, 3701 Locust Walk, Philadelphia, PA 19104, USA.

Received: 26 February 2020 Accepted: 30 November 2020

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