Design data extraction form

The design of the data extraction form was based on three important aspects: 1) the review questions, 2) the eligibility criteria of the selected studies, 3) the informal collation of experiences from numerous review authors (published in Cochrane Handbook for Systematic Reviews of Interventions [96]). Moreover, according to suggestions found on the Cochrane Handbook [96], ticking boxes or coded responses were adopted into the data extraction form. This was in order to save time during the data extraction, while it also ensured that the same term was used for data categorization during the extraction.

The data extraction form can be found in Appendix 2.5, while its components are discussed in the following sections.

a. General information

Information collected from the selected studies included: title, authors’ name, source information (year / volume / pages / journal or conference), contact E-mail address, country, the source type, study type (trial / observation / model), and data type (primary / secondary).

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•The contact E-mail address was collected as a mean to contact the author regarding possible queries.

•The country information was collected as a mean to identify the differences of the costing methods usage from country to country. Furthermore, the emphasis was put in UK studies, as information related with the costing methods and the data sources used in these studies was expected to be helpful at later stages of the research.

•The ‘price year’ was collected for comparison reason, as the cost value changes over time because of the inflation (for example, £20 in 1998 has not the same value as £20 in 2008). The price year information was useful for cost comparison at later stages of the current work.

•Information related with the study type and the data type was collected because they could help in assessment of the costing methodologies and the data sources that were used in the selected studies.

b. Participants

The following information was collected from the selected studies: total number (initial sample size / number of AML or APML patients – when AML/APML was not the only one study population), setting of target population (description of inclusion and exclusion criteria / diagnostic criteria / baseline characteristics/treatment phase), study period, outcome sample size (withdrawals and losses to follow-up).

•Three different sample sizes were collected. This was for two reasons. Firstly, the outcome sample size always differs from the initial numbers because of attrition or exclusions [96]. Secondly, if AML/APML was not the only study group (such as in case of hematological malignancy study), it was important to collect the number of AML/APML patients, as this number could affect the review results and its generalization.

•Age information was collected because AML/APML could occurred at any age [52, 53, 97, 98]. Also, since treatment types and treatment tolerance differed between age groups [52, 53, 97, 98], it was expected that differences in cost between age groups could occur. Therefore, it was deemed that age information collection was necessary.

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•Treatment phase information was collected because there were great different between treatment types and regimens in different treatments phases [97, 98], something that could the affect cost results.

•Study period’ was also collected as it was associated with the costing methods and the cost results.

c. Intervention

Information related with study intervention was also collected from the selected studies.

This included treatment type (overall treatment, chemotherapy, adjunctive treatment, transplantation, complication treatment, examination, supportive or palliative care), analysis type (Cost analysis, CEA/CUA), and objectives of selected studies.

•Treatment types information was collected because different treatments required different methods to cost. The information not only helped to categorize the selected studies, but also assisted in uncovering the costing methods/data sources used for costing different treatments.

•Objective information was collected because of its relation to the review questions. It not only helped to double check whether selected the studies were eligible, but also provided overviews of these studies.

d. Outcome (Costing Methods)

According to the review questions, the following information was collected: cost data sources (unit cost / charges / payments), cost drivers, costing methods, and cost results. It is worth noting that selected study results, mainly to be used as notes.

•Cost data source information was collected because it was the main part of the costing methods, and also it determined the cost results. Therefore, the collected information not only helped to uncover the costing methods that were used in the selected studies, but also helped to distinguish whether cost results were comparable.

•Information related with the costing method (such as method types, cost drivers, and data sources) was collected for three reasons. Firstly, it could uncover how previous studies measured the cost, which answered the review questions of the current review.

Secondly, it could help to assess whether any costs have been omitted in the selected

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studies. Thirdly, it could help to judge whether the study designs of the selected studies were applicable and replicable.

•The results of the selected study were collected because they provided a clear, albeit simple, overview of the studies (irrespectively of how many outcomes were presented).

Since variation in study results can be very large [99], it was decided only results that matched the review purposes to be collected.

e. Note

A blank footnote column was left for the purpose of keeping important notes relevant to the study. Also, following suggestions from the Cochrane Systematic review Handbook, another blank space was left for notes. This was placed near the beginning of the form, as opposed to its end, in order to avoid placing notes, questions or reminders in a position less noticeable [96]. Overall, two note-columns were included in the data extraction form.

Important notes (such as reminders) were put in the column positioned in the beginning of the form, while less important notes (such as reference to other studies) were put in the column in the end of the form.