“…As expected, all papers suffered from bias in their accuracy estimates of the index test from the use of an imperfect reference standard comparison, a well-known issue with comparative diagnostic accuracy studies [ 84 ]. The results of the quality assessment reviews conducted using the form adopted from CASP diagnostic study checklist showed that five papers [ 51 , 54 , 57 , 62 , 82 ] suffered from verification bias: not all patients received testing by both the index and the reference standard. In 38 papers [ 41 – 47 , 49 – 53 , 55 – 59 , 61 – 68 , 70 , 71 , 73 – 82 ], the results of the index test could have been influenced by the reference standard result.…”