Thread by @deeksj

Important paper in @bmj_latest from global leaders in test evaluation. Hope will improve quality of studies.
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Guidance for the design and reporting of studies evaluating the clinical performance of tests for present or past SARS-CoV-2 infection bmj.com/content/372/bm…

Thanks to @JennyDoust @KatyJLBell @leeflang_m
@jacdinnes @SallyJLord @SueMallett Janneke van de Wijgert, Sverre Sandberg, Khosrow Adeli,@pmmbossuyt Andrea Horvath for working on this with me. Its a team which covers all important aspects of test evaluation.

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From reading @DHSCgovuk @PHE_uk study reports and many others from organisations around the world, we are aware that the level of understanding about clinical test evaluation studies is often less than ideal.

This paper lays out clear steps to help improve.

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We keep on hearing "you can't expect perfect studies in a pandemic". But this isn't time to PAN*IC it is time to make sure we do things well so that the answers are both informative and likely to be true. It requires good planning and team input as is described here.

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This paper goes through 8 key points, and gives details relevant to Covid test studies. Brief summary below, much more detail and examples in the paper.

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#1: Define the intended use of the test
Many evaluations do not provide accurate estimates of because the relation between the purpose of the test, the selection of the study population, and the selection of the reference standard have not been carefully mapped out

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#2: Define the target condition—that is, what the test aims to detect. Potential target conditions include viral infection , covid-19 disease, infectiousness, immune response, viral clearance, past or recent infection, and immunity.

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#3: Define the population in which the test will be evaluated. Clinical performance studies should be conducted in individuals sampled from the population in which the test will be used, as determined by the intended use in step.

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#4: Describe the index test strategy
This may be one test, the same test repeated, or a combination of different tests. The entire testing pathway should be evaluated.

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#5: If applicable, describe which tests are compared and why
Decisions need to be made regarding the comparative performance of different tests. The comparison can be between different forms of testing, different tests of the same form, or different testing strategies.

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#6: Define the reference standard
The reference standard needs to clearly separate individuals who have the target condition from those who do not; those who have or have had the infection from those who do or have not, those who are infectious from those who are not

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#7: Analysis and presentation of results
Poor reporting of studies evaluating SARS-CoV-2 tests has been a common methodological concern in the studies to date. Reports should follow the STARD reporting guidelines for diagnostic accuracy studies.

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#8: Prospectively register the study protocol
Prospective registration is a sign of quality, provides evidence that the study objectives, test procedures, outcome measures, eligibility criteria, and data to be collected were defined prospectively, and supports transparency.

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We hope that this guide will help us get better evidence so that we can make informed to help use the right tests at the right times in the right patients.

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