In 1876, diagnoses based on observing clinical symptoms; if a patient responded positively to a disease-specific treatment, then they must have the disease.
Diagnostic testing began in 1882, when Paul Ehrlich observed that only the presence of typhoid bacillus (as identified with a certain dye) could prove a diagnosis of typhoid fever. Earlier diagnosis was based on the color of the skin.
This is how pharmaceuticals are manufactured in TEVA Hungary
Today, we determine medical conditions by studying disease markers or drugs residues that can be chemically detected in blood, urine, feces, saliva, and (since 2007) perspiration. Laboratory testing, sophisticated computer-assisted analytical instruments, and at-home testing all measure fundamental chemical reactions.