Table 1

Differences between grading of strength of accuracy and effectiveness evidence

ItemsEffectiveness researchAccuracy researchIssues to consider
The basics
QuestionParticipants, Intervention, Comparator and Outcome(s)Population, Index test and Reference standardPICO structure does not readily apply in diagnostic research
Study designRandomised controlled trial (RCT)
Non-randomised controlled studies
Other designs for index test and reference standard comparison
RCT not required for accuracy evaluations
Measure of performanceEffect estimate
(OR or
risk ratio)
Accuracy estimates
(sensitivity and
Accuracy estimates are usually paired; global single accuracy measures are not very intuitive
GRADE feature
Risk of biasTools for the risk of bias typically assess: random sequence generation, allocation concealment, blinding, incomplete outcome data, selective outcome reportingMethodological quality part QUADAS-2 instrument includes: participant selection, implementation of the index test, reference standard, flow and timingVarious tools exist; there is no consensus on what is best for accuracy research
IndirectnessBased on PICO question
(see above)
QUADAS-2 instrument applicability part can be deployedAccuracy research requires looking at participants, reference standard, flow and timing
InconsistencyI2 or χ² tests for heterogeneityVisual assessment of overlap of CIs between studiesAssessed separately for sensitivity and specificity in accuracy research
Imprecision95% CIs
around an effect measure
95% CIs around multiple accuracy measuresAssessed separately for sensitivity and specificity in accuracy research
Publication biasTest for funnel plot asymmetryTest for funnel plot asymmetryTest for funnel asymmetry requires particular caution in accuracy research
  • PICO, Population Intervention Comparator Outcome; GRADE, Grading of Recommendations Assessment, Development and Evaluation; QUADAS-2, Quality Assessment of Diagnostic Accuracy Studies.