This page contains a snapshot of featured content which highlights evidence addressing key clinical questions including areas of uncertainty. Please see the main topic reference list for details of all sources underpinning this topic.

BMJ Best Practice evidence tables

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Evidence tables provide easily navigated layers of evidence in the context of specific clinical questions, using GRADE and a BMJ Best Practice Effectiveness rating. Follow the links at the bottom of the table, which go to the related evidence score in the main topic text, providing additional context for the clinical question. Find out more about our evidence tables.

This table is a summary of the analysis reported in a guideline (underpinned by a systematic review) that focuses on the above important clinical question.

Confidence in the evidence is very low or low where GRADE has been performed and the intervention may be less effective or likely to be more harmful than the comparison for key outcomes. However, this is uncertain and new evidence could change this in the future.

Population: People with chronic cough and normal chest x-ray and physical examination

Intervention: Chest CT scan

Comparison: No chest CT scan

OutcomeEffectiveness (BMJ rating)?Confidence in evidence (GRADE)?

Diagnostic yield

See note ᵃ

Very Low

Recommendations as stated in the source guideline

We suggest that clinicians do not routinely perform a chest CT scan in patients with chronic cough who have a normal chest radiograph and physical examination.


ᵃ The content of this table is based on four observational studies. One prospective study found that the diagnostic yield of chest CT scan was 3/46 (6.5%) participants, while three retrospective studies produced the following results: 20/34 (58%) participants, 9/21 (43%) participants, and 21/59 (36%) participants.

The guideline task force noted that the variation in the above results, regarding the diagnostic yield of CT scan, were unlikely to explain the cause of coughs or influence treatment.

The guideline task force also noted that there is concern about the potential cancer risk from CT radiation exposure, particularly in children and women, which should be weighed against any diagnostic yields.

This evidence table is related to the following section/s:

Cochrane Clinical Answers

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Cochrane Clinical Answers (CCAs) provide a readable, digestible, clinically focused entry point to rigorous research from Cochrane systematic reviews. They are designed to be actionable and to inform decision making at the point of care and have been added to relevant sections of the main Best Practice text.

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