Define how combinations of clinical findings can be used to estimate probability. Symptoms or signs that make an independent contribution to the probability that a patient has a disease are identified and assigned numerical weights. Weights are based on statistical analysis of the findings contributions. Calculate the total score for the individual patient. Based on this total score place the patient in the appropriate subgroup with its associated probability of disease.
Some tests reduce uncertainty more than others do.
Measure the accuracy of tests. Most clinical laboratories consider values greater than 2 standard deviations from the mean as abnormal. Increasing the cut off levels would decrease the number of false positive but would increase the number of false negative. The test would be more specific but less sensitive. If the management of disease involves a high mortality rate cut off level for the diagnostic test should be adjusted to provide greater specificity.