Figure 1

Determining cutoff score for the four-point scoring system from coordinates of the receiver operating curve for highest sensitivity and specificity. The graph on the right is called a receiver operating characteristic curve (ROC curve). It is a plot of the true positive rate (y-axis) against the false positive rate (x-axis) for the different possible cut-points of a diagnostic test. The closer the curve is to the left-hand border and top border of the ROC space the more accurate the test. Accuracy is measured by the area under the curve. An area of 1 = perfect test; an area of 0.5 = inadequate test. The ROC curve analysis resulted in an area under the curve of 0.92 (95%CI 0.83 to 1.0), which is almost perfect and demonstrates excellent diagnostic accuracy. The table on the left outlines each individual plotted cut-point. At 23.5 the sensitivity was 0.84, with specificity of 1.0, and at 25 the sensitivity was 0.96, and specificity was 0.86. A cutoff point of 24 would therefore result in high sensitivity and specificity. 95%CI, ninety-five percent confidence interval.