Suppression of Substance Abuse Claims Distorts Medicaid Data

Nancy A. Melville

March 15, 2016

The Centers for Medicare and Medicaid Services's (CMS's) suppression of substance abuse-related claims from Medicaid searchable files corresponds with a sudden and significant decrease in rates of inpatient diagnoses for common substance abuse–related conditions. With potentially artificially low rates of some medical diagnoses, this finding could potentially skew results of scientific research.

"While it was previously apparent that CMSs' actions would hamper research on drug and alcohol abuse, our study demonstrates there may also be broader implications for the utility of the Medicaid data," first author Kathryn Rough told Medscape Medical News.

"More specifically, it appears the rate of claims for certain other medical conditions are systematically underestimated when using Medicaid data affected by the suppression policy," said Rough, of the Division of Pharmacoepidemiology and Pharmacoeconomics at Brigham and Women's Hospital and Harvard Medical School, in Boston, Massachusetts.

The study was published online March 15 in JAMA.

Patient Consent Policy

The suppression of all substance-related claims from CMS research-identifiable files was enacted to comply with a 1987 federal regulation prohibiting third-party payers from releasing information from federally funded substance abuse treatment programs without patient consent. The policy was not enacted until 2007.

Because all claims containing diagnostic or procedural codes related to substance abuse were removed, entire encounters captured in a claim were deleted, resulting in the suppression of important diagnoses linked to substance abuse.

Because Medicaid data are often used to conduct research, the investigators sought to determine the effect of the suppression policy on the rates of diagnoses of conditions linked to substance abuse that appeared in the Medicaid database.

The authors evaluated Medicaid data from 2000 to 2006, reflecting the period prior to implementation, and compared them with data from 2007 to 2010, the period after implementation.

The search focused on six conditions commonly linked to substance abuse ― hepatitis C, HIV, cirrhosis, tobacco use, depression, and anxiety. It also included conditions not typically associated with substance abuse ― type 2 diabetes, stroke, hypertension, and kidney disease.

Among 63 million inpatient claims that were identified, the results showed no significant difference between the two periods in terms of conditions unrelated to substance abuse.

Yet for conditions related to substance abuse, relative to rates observed in 2006, the decline following the implementation of the suppression policies was dramatic. There was a decline of 56.7% per 100,000 patients regarding hepatitis C (−1233; P < .001); a decline of 51.3% for tobacco use (−5015; P < .001); 48.9% for cirrhosis (−675; P < .001); 38.4% for depression (−2712; P = .02); 26.6% for anxiety (−795; P = .01); and 24.0% for HIV (−498; P < .001).

Among 13.6 billion outpatient claims, the declines were less dramatic. Although a negative level change was seen regarding all conditions associated with substance abuse, only anxiety showed a decline that was statistically significant, with a 6.3% reduction (−2512; P = .02).

"The absolute decreases in diagnosis rates are less pronounced in the outpatient setting, with the exception of the mental health diagnoses," Rough said. "This is probably due to differences in billing and coding practices in inpatient vs outpatient care."

The implications of the reduced rates seen after the data suppression are significant, potentially leading to spurious conclusions when using the data in research, said Rough.

"If investigators are unaware of the problem, they may get results that are misleading. For example, a hospital that regularly admits substance abusers will appear to have artificially low rates of readmission, giving a false appearance of better performance," she added.

Researchers using the Medicare and Medicaid research-identifiable files will need to make clear that the shortcomings constitute a limitation.

"It will be important for investigators using data from CMS to transparently report whether the data used in their study have been suppressed, as well as any steps that were taken to minimize the potential for bias," Rough said.

Reverse the Policy

The issue was also addressed in an article published in 2015 in the New England Journal of Medicine. The authors, Austin B Frakt, PhD, of the VA Boston Healthcare System, and Nicholas Bagley, JD, of the University of Michigan Law School, in Ann Arbor, argued that the suppression of the data could have far-reaching negative effects.

"Clearly, it is now infeasible to conduct any study of patients with substance-use disorders based on Research Identifiable Files, but studies of conditions disproportionately affecting such patients — such as hepatitis C or HIV — will also be hampered," they write.

Any study using those files is prevented from making full diagnosis-based risk adjustments that include substance use–disorder diagnoses, the authors added.

"Because the data have been altered in a systematic, nonrandom manner — with suppression affecting different populations, age groups, regions, and providers to different degrees — the results of many studies that have no apparent connection to substance use will be biased."

The authors call for action to reverse the policy.

"We believe that the federal government's short-sighted policy will harm the very people it was meant to protect," the authors note.

"We encourage SAMHSA and CMS, in dialogue with researchers and providers, to restore access to data that are necessary to improving care for patients with substance-use disorders."

The study received funding through grants from the Pharmacoepidemiology Program at the Harvard T. H. Chan School of Public Health, the National Institute of Allergy and Infectious Diseases, the National Institute of Mental Health, and the Eunice Kennedy Shriver National Institute of Child Health and Human Development. Kathryn Rough is recipient of a 3-month student internship from Bayer. One coauthor has received personal fees from AstraZeneca and the University of California, Berkeley, as well as grant funding from Pfizer.

JAMA. Published March 15, 2016. Abstract

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