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Lexchin J. Health Canada's use of its priority review process for new drugs: a cohort study. BMJ Open 2015;5:e006816.

The WHO ATC database was used to determine first-in-class status on the mistaken information that a first in class drug ended in a 01 number. After the paper was published the author was informed that this assumption was incorrect. Therefore, information from the United States Food and Drug Administration (contained in the new reference 10) was used instead to determine which drugs were first-in-class. The results from this reanalysis are quite similar and do not change the conclusions in the article.

Abstract – Data sources

Original: “World Health Organization Collaborating Centre for Drug Statistics Methodology”

New text: “United States Food and Drug Administration analysis of first in class new drugs”

Methods – Data analyses 5th paragraph

Original: “determined using the Anatomical Therapeutic Chemical (ATC) classification system from the World Health Organization {WHO Collaborating Centre for Drug Statistics Methodology, 2005 #18}. The 4th level ATC group for each drug was determined by searching the web site of the World Health Organization's Collaborating Centre for Drug Statistics Methodology. The 4th level is the chemical subgroup that the product belongs to. Drugs in the 4th level are listed in the order in which they appeared on the market and thus the first drug will have the numeral “01” at the end of its coding (10).”

New text: “based on an analysis of 645 new drugs approved by the United States Food and Drug Administration from 1987 to 2011.10

Results – 4th paragraph

Original: “There were 33 drugs that were first in class. Comparing Health Canada's rating to the evaluations by the PMPRB/Prescrire, the negative predictive value was 89.5% (95% CI 66.8, 98.4) and the positive predictive value was 57.1% (95% CI 28.9, 82.2)”

New text (changes in bold): “There were 98 drugs that were first in class. Comparing Health Canada's rating to the evaluations by the PMPRB/Prescrire, the negative predictive value was 91.2% (95% CI 80.7, 97.1) and the positive predictive value was 46.3% (95% CI 30.7, 62.6)”

Discussion – 2nd paragraph

Original: “After drugs that were second or later entries into a class were removed, there was still a large difference between Health Canada's negative predictive value (89.5%) and its positive predictive value (57.1%).”

New text (changes in bold): “After drugs that were second or later entries into a class were removed, there was still a large difference between Health Canada's negative predictive value (91.2%) and its positive predictive value (46.3%).”

Table 4

Original: The numbers in the table reading from left to right currently are:

1st row 8 6

2nd row 2 17

New numbers:

1st row 19 22

2nd row 5 52

References – number 10

Original: “WHO Collaborating Centre for Drug Statistics Methodology. About the ATC/DDD system Oslo: Norwegian Institute of Public Health; 2005 [updated January 14; cited 2005 June 30]. Available from: http://www.whocc.no/atcddd/.”

New text: “Lanthier M, Miller K, Nardinelli C, Woodcock J. An improved approach to measuring drug innovation finds steady rates of first-in-class pharmaceuticals. Health Affairs 2013;32:1433-9.”

Below the table the positive and negative predictive values currently are:

Positive predictive value=57.1% (95% CI 28.9, 82.2)

Negative predictive value=89.5% (95% CI 66.8, 98.4)

They should be:

Positive predictive value=46.3% (95% CI 30.7, 62.6)

Negative predictive value=91.2% (95% CI 80.7, 97.1)

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