GC-MS are used in newborn screening tests. These tests can find dozens of congenital metabolic diseases (also known as Inborn error of metabolism). GC-MS can determine compounds in urine even in very small amounts. These compounds are normally not present but appear in individuals suffering with metabolic disorders. This is becoming a common way to diagnose IEM for earlier diagnosis and beginning of treatment. This eventually leads to a better outcome. It is now possible to test a newborn for over 100 genetic metabolic disorders by a urine test at birth based on GC-MS.