- Background Cystic Fibrosis (CF) is an autosomal recessive condition caused by gene mutation which affects sodium and chloride transport across the membrane of secretory epithelial cells. New born screening for CF was introduced in the West Midlands, UK in November 2006. ~20% of CF patients may present with meconium ileus. The majority of the remainder are expected to be picked through new-born screening. Sweat test remains the gold standard for the diagnosis of CF and is a critical component of +ve newborn CF screening protocol. Aim To investigate the positive yield of sweat test at Queen’s Hospital Burton Upon Trent (in patients with negative new born CF screen) since the introduction of new born CF screening. Methods We retrospectively collected local data on all the sweat test results since the introduction of new born CF screening in the West Midlands. Results Out of 129 sweat tests performed, only one case yielded positive result (born before new born CF screening). Another patient had a borderline test result which was subsequently repeated and found to be normal. Therefore, we effectively have no positive sweat test results so far since the screening commenced. Conclusion Even though our data is encouraging and suggests increasing the threshold required for performing a sweat test (in individuals born after Nov 2006), this investigations should still be carried out in patients with high index of clinical suspicion as occasional cases will be missed despite universal new born CF screening programme.