Nonerosive reflux disease and functional heartburn are clearly separate entities.

[1]  E. Savarino,et al.  Impedance-pH reflux patterns can differentiate non-erosive reflux disease from functional heartburn patients , 2012, Journal of Gastroenterology.

[2]  E. Savarino,et al.  The added value of impedance-pH monitoring to Rome III criteria in distinguishing functional heartburn from non-erosive reflux disease. , 2011, Digestive and liver disease : official journal of the Italian Society of Gastroenterology and the Italian Association for the Study of the Liver.