NICE guidance on diagnosis and management of cystic fibrosis

Sweat Testing and Recent Advances

“…The sweat Cl − concentrations obtained from the wearable sensor showed excellent agreement with the conventional tests with a Pearson correlation coefficient of p = 0.97. Sweat Cl − measurements for all healthy subjects were within the accepted threshold for normal (≤29 mEq/L; [16][17][18][19][20][21][22][23][24][25][26][27], and all individuals with CF were above the accepted threshold (≥60 mEq/L; 65-130), confirming CF diagnosis. The correlation coefficient between the CFQT and conventional ST was 0.98 [95% confidence interval (CI): 0.97-0.99].…”

“…The most common gastrointestinal findings are failure to thrive with malabsorptive stools and recurrent abdominal pain. Patients with these findings should be referred to the ST center (7,(21)(22)(23).…”

“…It is also necessary to identify which CF patients are eligible for CF-mutation-specific therapy. The CFF recommends CF genotyping in all patients diagnosed with CF ( 7 , 11 , 12 , 21 ).…”

“…Sweat collection and analysis should be performed on the same day, and the results and their interpretation should be reported to clinicians as soon as possible. Analysis of the sweat shortly after collection or within a few hours should be routine procedure for the ST center ( 21 ). Collected sweat should not be stored or transported via the coiled tubing system because of the evaporation risk.…”

“…Sweat Cl − levels may also be elevated falsely in other pathologic conditions, including atopic dermatitis, ectodermal dysplasia, pseudohypoaldosteronism, untreated hypothyroidism, glycogen storage disease type I, carbonic anhydrase XII mutations, malnutrition, and anorexia nervosa. Elevated sweat Cl − concentrations in non-CF patients may also be related to iatrogenic causes, such as mineralocorticoid, NaCl − perfusion, and topiramate treatment ( 21 ). The underlying mechanism for false positive results in many conditions is unknown.…”