Lab Diagnosis: Sensitivity, Specificity and Predictive Values

[liveonearth]

sensitivity = ability of test to detect pts with specific disease. Get % by dividing those who have the dz and were detected by those who have the dz and were not detected. Subtract this % from 100 to get the false negative rate.

specificity = describes how well test abnormality is restricted to those who have dz. Get % by dividing those who tested positive and have dz, by those who tested positive and don't have it??? Subtract that % from 100 to get false positive rate.

predictive value

prevalence = % who have dz (in a pop) at given moment (if dz is rare then higher proportion of false positives is inevitable)

incidence = % of have dz in a year (in a population)

positive predictive value = PPV = those who have a gene for dz and test positive divided by all who test positive. Subtract this value from 100 to get chance of false positive.

negative predictive value = NPV = those who don't have gene and tested negative divided by all who tested negative. Subtract that value from 100 and get % who test negative and still have gene (false negative)

reproducibility = does the lab get same answer with same test on same specimen?

accuracy = is the test result correct, or wrong dt error?

normal range = usu given as mean +/- 2 standard deviations, but variation in population may not be gaussian distribution

statins --> rhabdomyolysis = rapid breakdown of skeletal muscle