In diagnosing cystic fibrosis, what initial findings are typically noted?

In diagnosing cystic fibrosis, the presence of bulky and greasy stools is a typical initial finding. This symptom arises due to malabsorption resulting from pancreatic insufficiency, a common feature of cystic fibrosis. The defective CFTR gene leads to thick, sticky mucus that blocks pancreatic ducts, preventing the proper digestion of fats and nutrients. Consequently, individuals with cystic fibrosis often experience steatorrhea, characterized by foul-smelling, greasy, and bulky stools.

Considering the other options, while severe malnutrition could be a result of cystic fibrosis due to malabsorption, it is not usually one of the first signs noted. Raised levels of IgA anti-tissue transglutaminase are indicative of celiac disease, for which the tests would not be related to cystic fibrosis. Frequent upper respiratory infections, although common in patients with cystic fibrosis, are more of a consequence of the disease rather than an initial diagnostic finding. The direct association of the stools' characteristics with pancreatic function makes the indicated answer the most relevant clinical sign for the diagnosis of cystic fibrosis.