PubMed has begun adding version numbers to its records.
To see an example search 20029611 in the PubMed search box; on the results screen click on the “other versions” link.
To search for all versions of a citation enter the PMID followed by .* e.g: 20029611.* This search brings up the first record entered into the database on August 31 and version two which gives a link to the related articles and more status information, in this case “Free PMC article”.
The version numbers will indicate revisions, updates to reviews, etc but not corrections (which have their own tags).