https://www.sciencedaily.com/releases/2018/06/180604160440.htm

"Even though access to this data was restored in 2017, it can be quite time consuming and costly to go back and fill in the gaps," says lead author and Dartmouth Institute research scientist Andrea Austin, PhD. "And, the reality is that redaction can and likely has affected a wide range of studies, beyond studies of addiction and opioid use disorder."

Using Medicare claims from 2012, the year before the redaction was implemented, the research team, created a new version of the 2012 cohort by removing any claim that included a substance abuse-related diagnosis or procedure code that was redacted in 2013. Then, to characterize how redaction might affect studies that utilized this data, they calculated the population rates of admission per 100 beneficiaries for selected diagnoses likely to be related to substance abuse, such as serious mental illness, depression, and hepatitis C. For comparison, they also calculated admission rates for diagnoses, such as diabetes, that are less likely be associated with substance-abuse (and thus less likely to be affected by redaction).