Sensitivity and Specificity

Editor – In the Authors’ Reply to the letter “Sensitivity and Specificity of Tests of Liver Injury”¹ in the November 2004 issue of Clinical Medicine & Research, the statement “It is true that no single test of liver injury is either highly sensitive or specific” would be more accurate if it read “It is true that no single test of liver injury is both highly sensitive and specific”. It is easy to come up with a test (for anything) that is either perfectly sensitive or perfectly specific; the test is of little use without some degree of both.