Objective:

To do a pilot study to determine the frequency and nature of published errata linked to RCTs in the MEDLINE database, and to estimate the proportion that are worthwhile obtaining.

Methods:

MEDLINE (SilverPlatter) was searched from 1995-2001/06 for records that had both 'randomized-controlled-trial' in the publication type field and 'erratum' in the comments field. (When a citable correction is published for an article that has a citation in MEDLINE, a reference to the published correction is added). Records from four journals (Lancet, BMJ, New England Journal of Medicine and JAMA) were downloaded, and 100 were randomly selected. The full articles and errata of the 100 records were examined by the author and assigned to one of three categories: 1. Yes - worthwhile acquiring, 2. Maybe - possibly worthwhile, 3. No - not worthwhile.
Also investigated were the number of errors mentioned per published erratum, the number of citations to the RCT and their erratum in the Science Citation Index, the time between publication RCTs and errata, and indexing of the errata in the Cochrane Controlled Trials Register (CCTR).

Results:

The 666 errata to RCTs were published in 295 different journals. 130 errata (19.5%) were published in just four journals; Lancet, BMJ, NEJM and JAMA. The average percentage of RCTs assigned errata was 1.2% over all journals, but 7.8% for these four journals. All RCTs and errata were in CCTR, but 77% of RCTs had one or more duplicate records in CCTR without the errata information. The Lancet, BMJ, NEJM and JAMA all provided free electronic access to errata, but many other journals did not.

The classification of errata gave:

1. Yes = 74%. Mostly in tables or figures.
2. Maybe = 9%. Mostly in the introduction or discussion.
3. No = 17%. Mostly errors in authorship.

Table 1. Characteristics of RCTs and errata

Characteristic measured Mean Median Max Min
Number of months between publication of the RCT and its erratum 3.5 3.0 26 1
Number of errors mentioned per published erratum. 1.6 1.0 6 1
Number of citations per year to the RCT 28.0 12.3 250 0
Number of citations per year to the erratum 0.6 0 8 0

Conclusions:

Errata were published for about 8% of RCTs in four major general medical journals, and most (74%) appeared to contain information important enough to be worthwhile obtaining. However, as most errata were never cited, this suggested they were largely ignored. To increase their visibility and access, it is recommended all journals provide free electronic access to errata and that the duplicate RCTs without errata information be removed from CCTR. This should facilitate access to more complete and accurate data for those using RCTs.