Diagnostic test: 4-field table

<p>A <strong>diagnostic test </strong>is a diagnostic instrument with a binary output or result: yes/no or positive/negative.</p> <p>The input state (condition) is also binary, e.g. healthy/diseased, not infected/infected, suitable/not suitable, etc.</p> <p>Both factors, <strong>condition</strong> and <strong>test result</strong>, are shown in a 4-field table. The outcome of the condition and test are 4 cells (2x2): true positive (TP) and false positive (FP) as well as true negative (TN) and false negative (FN).</p> <p>Depending on the reading - rows or columns - both <strong>sensitivity and specificity</strong> (pre-test probabilities) as well as <strong>positive and negative predictive value</strong> (post-test probabilities) can be read from the table.</p> <ul> <li>sensitivity: TP/(TP+FN)</li> <li>specificity: TN/(TN+FP)</li> <li>positive predictive value: &nbsp;TP/(TP+FP)</li> <li>negative predictive value: TN/(TN+FN)</li> </ul>