nasal potential difference measurement

Question

What tests can be done to determine the severity of the disease? Where it canbe performed measurement of nasal potential difference and what is the correlation between disease severity and this analysis?

Answer

Hello,
first of all, we would like to do some general comments on the NPD:

The NPD test is test that directly measures the activity of the CFTR channel in the nose. It is mainly used to assist in the diagnosis of CF when other tests such as sweat test and DNA analysis are inconclusive. Normal values and values typically found in patients with CF are available for all test components: basal measurement, changes when blocking sodium secretion and stimulating chloride secretion.

The test is not used to determine disease severity in a specific person. In cross sectional studies, there is however some correlation between the test results and the disease severity: the mean test results become increasingly abnormal when one goes from a group of patients with atypical CF over a group of patients with pancreas sufficiency to a group of patients with pancreas insufficiency. But we must stress that there is a lot of overlap.

Since the test measures CFTR function in the respiratory system, it is also used in research to evaluate drugs that aim to cure CF by improving the CFTR function. Indeed, the NPD result improved significantly when ivacaftor, the drug for patients carrying the G551D mutation was tested. Also the sweat test is used for that purpose.

Now to our specific situation in Romania:
At one point, we performed the test in our center, but for some technical reasons we gave up. In Romania this test is not performed now, sweat test is the standard test used in our country and abroad for cystic fibrosis diagnosis, conform with European Cystic Fibrosis Society criteria .
Regards, Prof.Dr Liviu Pop and Prof. Kris de Boeck

04.01.2012