Objective: To review the literature on postnasal drip syndrome (PNDS)-induced cough and the various causes of PNDS. Hereafter, PNDS will be referred to as upper airway cough syndrome (UACS).
Methods: MEDLINE search (through May 2004) for studies published in the English language since 1980 on human subjects using the medical subject heading terms "cough," "causes of cough," "etiology of cough," "postnasal drip," "allergic rhinitis," "vasomotor rhinitis," and "chronic sinusitis." Case series and prospective descriptive clinical trials were selected for review. Also, any references from these studies that were pertinent to the topic were obtained.
Results: In multiple prospective, descriptive studies of adults, PNDS due to a variety of upper respiratory conditions has been shown either singly or in combination with other conditions, to be the most common cause of chronic cough. The symptoms and signs of PNDS are nonspecific, and a definitive diagnosis of PND-induced cough cannot be made from the medical history and physical examination findings alone. Furthermore, the absence of any of the usual clinical findings does not rule out a response to treatment that is usually effective for PND-induced cough. The differential diagnosis of PNDS-induced cough includes allergic rhinitis, perennial nonallergic rhinitis, postinfectious rhinitis, bacterial sinusitis, allergic fungal sinusitis, rhinitis due to anatomic abnormalities, rhinitis due to physical or chemical irritants, occupational rhinitis, rhinitis medicamentosa, and rhinitis of pregnancy. Because of a high prevalence of upper respiratory symptoms associated with gastroesophageal reflux disease (GERD), GERD may occasionally mimic PNDS. A crucial unanswered question is whether the conditions listed above actually produce cough through a final common pathway of PND or whether, in fact, in some circumstances they cause irritation or inflammation of upper airway structures that directly stimulate cough receptors and produce cough independently of or in addition to any associated PND.
Conclusion: PNDS (ie, UACS) secondary to a variety of rhinosinus conditions is the most common cause of chronic cough. Because it is unclear whether the mechanisms of cough are the PND itself or the direct irritation or inflammation of the cough receptors located in the upper airway, the guideline committee has decided that, pending further data that address this difficult question, the committee unanimously recommends that the term upper airway cough syndrome be used in preference to postnasal drip syndrome when discussing cough associated with upper airway conditions.