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Peterson K, McDonagh M, Carson S, et al. Drug Class Review: Newer Antiemetics: Final Report Update 1 [Internet]. Portland (OR): Oregon Health & Science University; 2009 Jan.

Methods

Literature Search

To identify relevant citations for the original report, we searched the Cochrane Central Register of Controlled Trials (4th Quarter 2004), Cochrane Database of Systematic Reviews, MEDLINE (1966 to week 1 of February 2005), EMBASE (2nd Quarter 2005), and CancerLit (1974 to March 2005) using terms for included drugs, indications, and study designs (see Appendix D for complete search strategies). For update 1, we searched Medline (1996 to week 2 of 2008), Cochrane Central Register of Controlled Trials (2nd Quarter 2008), Cochrane Database of Systematic Reviews (1st Quarter 2008), and Database of Abstracts of Reviews of Effects (DARE) (2nd Quarter 2008). These searches were repeated in October 2008 in Medline and 3rd Quarter 2008 in Cochrane and DARE Databases to identify any additional publications published before the draft report was finalized. We have attempted to identify additional studies through searches of reference lists of included studies and reviews, the Food and Drug Administration website, and dossiers submitted by pharmaceutical companies for the current review. All citations were imported into an electronic database (EndNote XI).

Study Selection

Using the criteria listed above, two reviewers independently assessed abstracts of citations identified from literature searches for inclusion, Full-text articles of potentially relevant abstracts were retrieved, and a second review for inclusion was conducted by reapplying the inclusion criteria.

Data Abstraction

The following data were abstracted from included trials: study design; setting; population characteristics (including sex, age, ethnicity, diagnosis); eligibility and exclusion criteria; interventions (dose and duration); comparisons; numbers screened, eligible, enrolled, and lost to follow-up; method of outcome ascertainment; and results for each outcome. We recorded intention-to-treat results when reported. In cases where only per protocol results were reported, we calculated intention-to-treat results if the data for these calculations were available. In trials with crossover, outcomes for the first intervention were recorded if available. This approach controlled for the potential for biased results caused by differential withdrawal before crossover and for the possibility of either a “carryover effect” (from the first treatment) in studies without a washout period or a “rebound effect” from withdrawal of the first intervention.

Data abstracted from observational studies included design; eligibility criteria; duration; interventions; concomitant medication; assessment techniques; age, gender, and ethnicity; number of patients screened, eligible, enrolled, withdrawn, or lost to follow-up; number of patients analyzed; and results.

Validity Assessment

We assessed the internal validity (quality) of trials with the predefined criteria listed in Appendix E. These criteria are based on the US Preventive Services Task Force and the National Health Service Centre for Reviews and Dissemination (United Kingdom) criteria.18, 19 We rated the internal validity of each trial based on the methods used for randomization, allocation concealment, and blinding; the similarity of compared groups at baseline; maintenance of comparable groups; adequate reporting of dropouts, attrition, crossover, adherence, and contamination; loss to follow-up; and the use of intention-to-treat analysis. Trials that had a fatal flaw were rated “poor-quality”; trials that met all criteria were rated “good-quality”; the remainder were rated “fair-quality.” As the fair-quality category is broad, studies with this rating vary in their strengths and weaknesses: The results of some fair-quality studies are likely to be valid, while others are only probably valid. A poor-quality trial is not valid—the results are at least as likely to reflect flaws in the study design as the true difference between the compared drugs. A fatal flaw is reflected by failure to meet combinations of items of the quality assessment checklist.

External validity of trials was based on whether the publication adequately described the study population, how similar patients were to the target population in whom the intervention would be applied, and whether the treatment received by the control group was reasonably representative of standard practice. We also recorded the role of the funding source.

Overall quality ratings for an individual study were based on internal and external validity ratings for that trial. A particular randomized trial might receive 2 different ratings: 1 for effectiveness and another for adverse events. The overall strength of evidence for a particular key question reflects the quality, consistency, and power of the set of studies relevant to the question.

Included systematic reviews were also rated for quality based on predefined criteria (see Appendix E) based on clear statement of the questions(s) and inclusion criteria, adequacy of search strategy, validity assessment and adequacy of detail provided for included studies, and appropriateness of the methods of synthesis.

Data Synthesis

We constructed evidence tables showing the study characteristics, quality ratings, and results for all included studies. Trials that evaluated 1 newer antiemetic against another provided direct evidence of comparative effectiveness and adverse event rates. Where possible, these data are the primary focus. In theory, trials that compare newer antiemetic to other drug classes or placebos can also provide evidence about effectiveness. This is known as an indirect comparison and must be interpreted with caution for a number of reasons, mainly issues related to heterogeneity between trial populations, interventions, and assessment of outcomes. Data from indirect comparisons are used to support direct comparisons, where they exist, and are also used as the primary comparison where no direct comparisons exist.

Quantitative analyses were conducted using StatsDirect (Version 2.7.0, 7/7/2008) for meta-analyses of outcomes reported by a sufficient number of studies and for combining results of studies that were homogeneous enough that combining their results could be justified. When quantitative analyses were not possible, the data were summarized qualitatively.

Peer Review and Public Comment

Original Drug Effectiveness Review Project reports are independently reviewed and commented upon by 3 to 5 peer reviewers. Peer reviewers are identified through a number of sources, including but not limited to professional society membership, acknowledged expertise in a particular field, prominent authorship in the published literature, or recommendation by Drug Effectiveness Review Project participating organizations. A list of individuals who have acted as peer reviewers of Drug Effectiveness Review Project reports is available on the Drug Effectiveness Review Project website.

Peer reviewers have a maximum of 3 weeks for review and comment. They are asked to submit their comments in a standardized form in order to maintain consistent handling of comments across reports and to allow the Drug Effectiveness Review Project team to address all comments adequately. The original antiemetics report was reviewed by 4 content and methodological experts prior to finalization. The Drug Effectiveness Review Project process allows for a 2-week public comment period prior to finalization of the report. Draft reports are posted on the Drug Effectiveness Review Project website and interested individuals or organizations can review the complete draft report and submit comments. Comments from peer reviewers and the public are entered into a spreadsheet and the disposition of each comment is tracked individually.

Copyright © 2008, Oregon Health & Science University, Portland, Oregon.
Cover of Drug Class Review: Newer Antiemetics
Drug Class Review: Newer Antiemetics: Final Report Update 1 [Internet].
Peterson K, McDonagh M, Carson S, et al.
Portland (OR): Oregon Health & Science University; 2009 Jan.

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