Re: positive sweat test x 2 but no cf gene why
I to have a daughter with elevated sweat chloride results and no known genes. She has classic CF signs and was diagnosed years ago despite her very shy genes.
If your son has symptoms and the medicines and therapy help him, I would certainly keep doing them.
They do not know everything about CF. In fact, it is changing at lighting speed....
I would not necessarily rule CF out based on your sons test results...
Nasal Potential Difference
The impaired ion transport of CF respiratory epithelia can be studied in vivo by measuring the potential difference (NPD) in nasal mucosa.47 This is a significantly more complex test of CFTR function than measurement of sweat electrolytes. The protocol for NPD is well described and standardised but performed in only specialised (mostly adult) centres.48 Patients with CF have reduced chloride transport with sodium hyperabsorption, measured as a more negative basal potential difference. Perfusion with the sodium channel blocker amiloride results in a greater drop in NPD in CF patients, while perfusion with chloride-free solution and isoproterenol to stimulate CFTR function has no effect. NPD may complement sweat testing and CFTR mutation analysis.
However, it may also produce indeterminate results, particularly in “borderline” cases.49,50 NPD measurement is technically difficult and requires extensive experience for proper conduct and interpretation.51 Only one centre has reported use of NPD in infants.52 The presence of nasal inflammation, as in allergic rhinitis or viral infection, can alter ion transport and result in false negative results.48
For patients in whom both the sweat test and mutation analysis are inconclusive, an abnormal nasal PD measurement can be used as evidence of CFTR dysfunction.38
Last edited by moderator2; 11-17-2010 at 04:59 AM.