With the advancement of molecular biology, a number of genetic biomarkers are being discovered to detect diseases. Therefore it is important to understand their judicious use, especially for rheumatic diseases and cancers as their treatment is costly. Validity of a test is the ability to measure what it is supposed to measure. We need to test the following parameters before including the biomarker testing in our diagnostic protocols.
Analytical validity- It depends upon the sensitivity and specificity of a biomarker predicting the disease, eg, anti-dsDNA for SLE is specific and will rule out the true negatives ie. those who don't have the disease whereas anti-nuclear antibody is sensitive and might increase false positives ie those who have the antibody but are not suffering from SLE. If the disease burden is high in the community, the biomarker must be sensitive. If not, it should be…
