Abstract:
When the need arises to identify a disease,
substitute tests or screening tests are commonly used to
recommend patients for its respective “Gold Standard”. Since
it is seldom that these gold standards are carried out for those
who pass the substitute tests, calculating the sensitivity and
specificity of the substitute test has become a near impossible
task using conventional methods. However, due to the life
threatening nature of certain diseases such as coronary artery
disease (CAD), understanding the effectiveness of these
substitute tests in detecting the disease for sub-regions of
the world is of utmost importance. Therefore, the primary
objective of this study was to develop a theoretical framework
to determine the sensitivity and specificity of a diagnostic test
in the presence of severe missingness in the results of its gold
standard.
The methodology involves missing value imputation for the
missing response, which is the result of the gold standard for
those who have passed the substitute test. Logistic models were
used to predict the existence of the disease using pre-defined
risk factors. Subsequently, receiver operator characteristic
(ROC) curves were used to confirm the existing cut-off for the
substitute test.
This procedure is illustrated on data from a retrospective
study carried out in a General Hospital in Sri Lanka. The
ROC curve analysis verified the existing Bruce protocol
method cut-off as being the best to classify the existence of
CAD. The study confirms that the results conform to world
standards.
