Abstract
This is the ninth in a series of articles on making evidence-based medicine work for you. The series is based on the book ‘Attenti Alle Bufale’ by Tom Jefferson (www.attentiallebufale.itb)
Quick Instrument
If a letter presents original data, keep it in mind but beware as you will not have visibility of methods. If the letter offers an alternative view of a paper or an editorial you may also wish to read it. If there is no declaration of conflicts of interest, bin it. Regard all letters as opinions until proven otherwise.
Full Instrument
If you are able to identify and access the data source, apply the relevant Bufala-spotting short and full instruments.
Rationale
Letters contain opinions, often supporting or criticizing a piece in the journal. At times letters may indicate the existence of a study or of data which have been suppressed (publication bias). Writing to the author will soon clarify the issue.