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help for quadas                                           (Ben Adarkwa Dwamena)

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quadas: Graphical depiction of quality assessment in diagnostic accuracy review
> s

Syntax

        quadas varlist [if exp] [in range] [, options *]

        +---------+
    ----+ OPTIONS +----------------------------------------------------------

        sum creates a figure summarizing compliance of individual studies
        with methodologic quality items (varlist) scored yes, unclear, or no

        bar plots a bar graph of overall frequency of compliance with
        methodologic quality items (varlist) scored yes, unclear, or no

        color bar or summary graph generated in color with yes=green,
        unclear=yellow and no=red.

        may use graph editor or other twoway options to edit default
        appearance.

Remarks

        Quality assessment of primary studies in systematic reviews assist in
        identifying potential sources of bias and to limit the effects of
        these biases on the estimates and the conclusions of the review.
        Quality appraisal offers a general impression of the validity of the
        available evidence. The Cochrane Diagnostic Test Accuracy Working
        Group recommends the QUADAS (Quality Assessment of Diagnostic
        Accuracy Studies) checklist to assess the quality of diagnostic test
        accuracy studies. QUADAS is a rigorously constructed and validated
        tool that can be used by investigators undertaking new systematic
        reviews. The QUADAS tool consists of 14 items that cover patient
        spectrum, reference standard, disease progression bias, verification
        and review bias, clinical review bias, incorporation bias, test
        execution, study withdrawals, and intermediate results.

        The results may be summarized using:

        (1) Methodological quality graph(example appended Quadas1.pdf):
        review authors' judgments about each methodological quality item for
        each included study.

        (2) Methodological quality summary(example appended Quadas2.pdf):
        review authors' judgments about each methodological quality item
        presented as percentages across all included studies

        Although not implemented in quadas, 1n the analysis phase of
        systematic review, the results of the quality appraisal may guide
        explorations of the sources of heterogeneity. Possible methods to
        address quality differences are sensitivity analysis, subgroup
        analysis, or meta-regression analysis, although the number of
        included studies may often be too small for meaningful
        investigations. Also, incomplete reporting hampers any evaluation of
        study quality.

Examples

        use http://sitemaker.umich.edu/metadiagnosis/files/quadas.dta

        Methodolgical Quality Graph

        quadas spect select ref incorp testdesc refdesc blintest blinref clin
            indeterm withdraw, bar col

        Methodolgical Quality Summary

        quadas spect select ref incorp testdesc refdesc blintest blinref
            clin, id(studid) sum col ysiz(7) xsiz(4)


References

        Whiting P, Rutjes AW, Reitsma JB, Bossuyt PM, Kleijnen J.  The
        development of QUADAS: a tool for the quality assessment of studies
        of diagnostic accuracy included in systematic reviews.  BMC Med Res
        Methodol 2003;3:25

        Leeflang MM, Deeks JJ, Gatsonis C, Bossuyt PM, Cochrane Diagnostic
        Test Accuracy Working Group.  Systematic reviews of diagnostic test
        accuracy.  Ann Intern Med. 2008;149(12):889-897

Author

        Ben A. Dwamena, Division of Nuclear Medicine, Department of
        Radiology, University of Michigan, USA Email bdwamena@umich.edu for
        problems, comments and suggestions

Citation

        quadas is not an official Stata command. It is a free contribution to
        the research community, like a paper.  Suggested citation if using
        quadas in published work:

        Dwamena, Ben A.(2010) quadas: A program for graphical depiction of
        study quality assessment for diagnostic test accuracy reviews.
        Division of Nuclear Medicine, Department of Radiology, University of
        Michigan Medical School, Ann Arbor, Michigan.