In the international context, The majority of people with CF are diagnosed by age 2 thanks to newborn screening tests. However this is not the case in India
For children and adults, Diagnosing cystic fibrosis is a multistep process.
First step is the evaluation of symptoms as presented by a clinic examination
Second is a sweat test. Wherein an electric current is used to drive pilocarpine into the skin, stimulating sweating. The sweat is collected and analyzed for salt levels. Having unusually high levels of chloride in the sweat suggests CFTR is dysfunctional. As per the standards accepted to most doctors. Sweat chloride level above 40 is suspect of Cystic Fibrosis, While sweat chloride above 60 is a diagnosis of cystic fibrosis. In India, access to the sweat test itself is a challenge owing to cost and lack of availability at least in up country areas. Most diagnosis amongst less affording patients in India stops at this stage.
Third, and most confirmative of testing is Genetic testing. It is used to identify the CFTR mutations typically associated with cystic fibrosis. Many laboratories can test for the 30–96 most common CFTR mutations, which can identify over 90% of people with cystic fibrosis
For infants, a complete diagnostic evaluation includes a newborn screening, a sweat chloride test. a genetic or carrier test, and a clinical evaluation