The sweat test may not work well in newborns because they do not produce enough sweat. In the IRT test, blood drawn 2 to 3 days after birth is analyzed for a specific protein called trypsinogen. Positive IRT tests must be confirmed by sweat and other tests. Also, a small percentage of people with CF have normal sweat chloride levels. They can only be diagnosed by chemical tests for the presence of the mutated gene.
Genes are the basic units of heredity.
They are located on structures within the cell nucleus called chromosomes. The function of most genes is to instruct the cells to make particular proteins, most of which have important life-sustaining roles. A mutation can cause the body to make a defective protein or no protein at all. The result is a loss of some essential biological function and that leads to disease. Children may inherit altered genes from one or both parents.