Table 2Inclusion and exclusion criteria

Study CharacteristicInclusion CriteriaExclusion Criteria
  • Humans
  • KQ 1: Patients with cough (any duration)
  • KQ 2:
    • Patients with chronic cough (persisting 4 weeks if <14 years of age or 8 weeks if ≥ 14 years of age, or as stated by study authors)
    • Patients with unexplained or idiopathic, unresponsive, refractory, intractable, or uncertain chronic cough
  • Subgroups of potential interest include:
    • Age (the elderly, children <6 years of age, children <2 years of age)
    • Pregnant women
    • Women
    • Underlying etiologies (asthma, GERD, UACS, tobacco use, ACE inhibitor use, pulmonary infection, bronchitis, cystic fibrosis, others)
    • Immunocompromised patients
    • Patients with a history of substance abuse
KQ 2:
  • Patients with chronic cough of known etiology undergoing specific therapy
  • Patients with cough resulting from invasive respiratory tract instrumentation (e.g., ventilator dependent, tracheostomy, endotracheal intubation)
  • KQ 1: Qualitative and quantitative instruments used to assess cough (e.g., general and cough-specific HRQOL instruments, visual analog scales, objective cough counting, tussigenic challenge, exhaled nitric oxide)
  • KQ 2: Nonspecific symptomatic treatment of cough with:
    • Antitussive medications such as opiates (codeine, hydrocodone), dextromethorphan, and respiratory anesthetics (benzonatate)
    • Protussive medications such as expectorants (guaifenesin) and mucolytic or mucus-modifying agents (acetylcysteine, dornase alfa inhaled)
    • Nonpharmacological treatments such as chest physiotherapy, herbal remedies, aroma therapy, acupuncture, humidifiers, medicated vapors, alcohol, honey, speech therapy
KQ 2:
  • Medications that are not commercially available globally or have been pulled from the market worldwide. Note that we did not exclude medications that are not commercially available within the United States but are available elsewhere
  • KQ 1 (instruments): Other instruments; the proposed reference standard will be cough counts
  • KQ 2 (interventions): All of the above-listed interventions compared both within class and across classes, and including placebo for mixed meta-analysis
  • KQ 1: Study assesses an outcome of interest:
    • Diagnostic accuracy (e.g., sensitivity, specificity, positive predictive value, negative predictive value, validity, reliability, responsiveness, feasibility)
    • Therapeutic efficacy (e.g., change in clinical practice, impact on patient or provider decisionmaking)
    • Patient outcome efficacy (e.g., acceptability, quality of life, chest pain, depression, or anxiety)
  • KQ 2: Study assesses an outcome of interest:
    • Cough symptoms
    • Cough severity
    • Cough frequency
    • Complications related to coughing
    • Functional status
    • Health-related quality of life (generic or cough-specific)
    • Health care utilization and costs
    • Adverse effects of antitussive, protussive, and nonpharmacological interventions including sleep disturbance, allergic reaction, drowsiness, headache, chest pain, dizziness, rash
KQ 2:
  • Study assesses outcomes only using induced sputum (relevant only to patients with wet or productive cough), or BPC (measures hyperresponsiveness relevant to measuring lower airway reactivity to diagnose asthma)
  • Timing of followup was not limiteda
  • Inpatient and outpatient
Study design
  • KQ 1 (instruments): Evaluation studies
  • KQ 2 (interventions): RCTs, cohort studies
  • All sample sizes
  • Not a clinical study (e.g., editorial, non–systematic review, letter to the editor, case series)
  • KQ 2: Case-control studies
  • English-language only
  • Peer-reviewed articles
  • Relevant systematic review, meta-analysis, or methods article (used only for background and as potential sources of additional relevant material)
  • Non-English-language publicationsb

ACE = angiotensin-converting enzyme; BPC = bronchoprovocation challenge; GERD = gastroesophageal reflux disease; HRQOL = health-related quality of life; KQ = Key Question; RCT = randomized controlled trial; UACS = upper airway cough syndrome


For all included studies, we indicate the total number of patients enrolled and longest length (weeks or months) of followup, if relevant.


Given the high volume of potentially relevant literature available in English-language publications, the planned focus of our review on therapies actively used within the United States, and the scope of our current KQs, non-English-language articles were excluded.

From: Methods

Cover of Assessment and Management of Chronic Cough
Assessment and Management of Chronic Cough [Internet].
Comparative Effectiveness Reviews, No. 100.
McCrory DC, Coeytaux RR, Yancy WS Jr, et al.

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