Definitions for the level of evidence, strength of recommendation, and net benefit follow the "Major Recommendations."
Table: Uncommon Causes of Cough*
Causes of Cough |
Pulmonary disorders**
Tracheobronchomalacia Airway stenosis/strictures Tracheobronchopathia osteoplastica Mounier-Kuhn syndrome (tracheobronchomegaly) Tracheobronchial amyloidosis Airway foreign bodies Broncholithiasis Lymphangioleiomyomatosis Pulmonary Langerhans cell histiocytosis Pulmonary alveolar proteinosis Pulmonary alveolar microlithiasis High altitude Tonsillar hypertrophy Mediastinal masses Pulmonary edema Pulmonary embolism Drug-induced cough Miscellaneous (e.g., vocal cord dysfunction, surgical sutures in airways)
Nonpulmonary disorders
Connective tissue disorders*** Vasculitides (e.g., WG, GCA, and RPC) Esophageal disorders (tracheoesophageal and bronchoesophageal fistula) Inflammatory bowel diseases (e.g., Crohn's disease and ulcerative colitis) Thyroid disorders (goiter, thyroiditis) Others (e.g., Tourette syndrome)
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*WG = Wegener granulomatosis; GCA = giant cell arteritis (temporal arteritis); RPC = relapsing polychondritis.
**Conditions in which cough is a major symptom (present in >50% of patients) or a presenting symptom.
***These include rheumatoid arthritis, systemic lupus erythematosus, scleroderma, Sjogren syndrome, mixed connective tissue disease, relapsing polychondritis.
- In patients with chronic cough, uncommon causes should be considered when cough persists after evaluation for common causes and when the diagnostic evaluation suggests that an uncommon cause, pulmonary as well as extrapulmonary (see Table above, titled "Uncommon Causes of Cough"), may be contributing. Level of evidence, low; benefit, substantial; grade of recommendation, B
- In patients with chronic cough, until uncommon causes that potentially may be contributing to the patient's cough have been ruled out, the diagnosis of unexplained cough should not be made. Level of evidence, low; benefit, substantial; grade of recommendation, B
- If cough persists after consideration of the most common causes, perform a computed tomography (CT) scan and, if necessary, a bronchoscopic evaluation. Level of evidence, low; benefit, substantial; grade of recommendation, B
- In patients who present with abrupt onset of cough, consider the possibility of an airway foreign body. Level of evidence, low; benefit, substantial; grade of recommendation, B
- In patients with unexplained cough, evaluate the possibility of drug-induced cough. Level of evidence, low; benefit, substantial; grade of recommendation, B
- In patients with unexplained cough, consider a therapeutic trial of withdrawing the drug that is suspected to cause the cough. Level of evidence, low; benefit, substantial; grade of recommendation, B
Definitions:
Quality of the Evidence
Good = evidence is based on good randomized controlled trials (RCTs) or meta-analyses
Fair = evidence is based on other controlled trials or RCTs with minor flaws
Low = evidence is based on nonrandomized, case-control, or other observational studies
Expert opinion = evidence is based on the consensus of the carefully selected panel of experts in the topic field. There are no studies that meet the criteria for inclusion in the literature review.
Strength of Recommendations
A = strong recommendation
B = moderate recommendation
C = weak recommendation
D = negative recommendation
I = no recommendation possible (inconclusive)
E/A = strong recommendation based on expert opinion only
E/B = moderate recommendation based on expert opinion only
E/C = weak recommendation based on expert opinion only
E/D = negative recommendation based on expert opinion only
Net Benefit
Substantial = There is evidence of benefit that clearly exceeds the minimum clinically significant benefit and evidence of little harm
Intermediate = Clear evidence of benefit but with some evidence of harms, with a net benefit between that defined for "substantial" and "small/weak"
Small/weak = There is evidence of a benefit that may not clearly exceed the minimum clinically significant benefit, or there is evidence of harms that substantially reduce (but do not eliminate) the benefit such that it may not clearly exceed the minimum clinically significant benefit
None = Evidence shows that either there is no benefit or the benefits equal the harms
Conflicting = Evidence is inconsistent with regard to benefits and/or harms such that the net benefit is uncertain
Negative = Expected harms exceed the expected benefits to the population
Table: Relationship of Strength of the Recommendations Scale to Quality of Evidence and Net Benefits
|
Net Benefit |
Quality of Evidence |
Substantial |
Intermediate |
Small/Weak |
None |
Conflicting |
Negative |
Good |
A |
A |
B |
D |
I |
D |
Fair |
A |
B |
C |
D |
I |
D |
Low |
B |
B |
C |
I |
I |
D |
Expert Opinion |
E/A |
E/B |
E/C |
I |
I |
E/D |