HLA-B27 in 1982: Reappraisal of a Clinical Test

Excerpt

The practice of medicine may be regarded as a beneficent union of art and science, but many physicians feel uncomfortable with its metaphysical or mathematical aspects. In an article in this issue Khan and Khan (1) discuss probability reasoning in clinical decision making, using a mathematical formula introduced in the 18th century by the Reverend Thomas Bayes. The authors explain that the human leukocyte antigen (HLA) B27 test provides a probability statement regarding the existence of disease, pointing out that the test is most useful for physicians who understand the concept of a priori (pre-test) and a posteriori (post-test) probabilities