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Table 2 Quality assessment of the DOK study design (QUADAS-2)

From: Challenges in diagnostic accuracy studies in primary care: the fecal calprotectin example

Signaling questions Answer Risk of bias/applicability Planned adjustment
Domain 1: Patient selection    
Risk of bias   Low risk  
Is a consecutive sample of patients enrolled? Yes   
Is a case-control design avoided? Yes   
Does the study avoid inappropriate exclusions? Yes   
Applicability   High concern - Magnitude will be evaluated
Are there concerns that the included patients and setting do not match the topic of our study (patients had symptoms suggestive of inflammatory bowel disease in primary care)?    
Domain 2: Index test    
Risk of bias   Low Risk  
Are the index test results interpreted without knowledge of the results of the reference standard? Yes   
If a threshold was used, is it pre-specified? Yes   
Applicability   Low Concern  
Are there concerns that the index test, its conduct, or interpretation differ from the topic of our study (fecal calprotectin was measured with ELISA)?    
Domain 3: Reference standard    
Risk of bias   High risk  
Is the reference standard likely to correctly classify the target condition? No   - Probably not clinically relevant
- Adjustment in analysis [30, 31]
Are the reference standard results interpreted without knowledge of the results of the index test? Yes   
Domain 4: Flow and timing    
Risk of bias   High risk  
Is there an appropriate interval between index test and reference standard? No   - Represents care as usual
- Repeated measurement index test before endoscopy
Do all patients receive a reference standard? Yes   
Do all patients receive the same reference standard? No   - Adjustment in analysis [30, 31]