Study examination bias relates to the
exclusion of technically limited or incomplete
studies or the prospective inclusion
of only patients who are deemed
competent to produce a technically adequate
examination (19). This bias will
result in an overestimation of sensitivity,
and specificity may increase because
false-positive “artifacts” are decreased.
For example, in a study to evaluate renal
MR angiography versus conventional
angiography, if only subjects are
included who can adequately suspend
respiration during MR imaging, the performance
of MR angiography will be
overestimated. As Begg and McNeil
(26) assert, if a test is not repeatable,
the analytic treatment should be similar
to that for equivocal test results. Uninterpretable
test results should not be
discarded, and at the minimum their
frequency should be reported