Opioid-Related Deaths Underestimated Because of Incomplete Reporting, Study Says

Allison Inserro

States may be underestimating the effect of opioid-related overdose deaths because of incomplete cause-of-death reporting on death certificates, indicating that the mortality from opioids may be higher than it appears, according to an analysis published Wednesday.

The study, published in Public Health Reports, the journal of the Office of the US Surgeon General, found that potentially 70,000 opioid-related overdose deaths were not included in national opioid-related mortality estimates from 1999 to 2015 because coroners and medical examiners did not specify the drug that contributed to the cause of death. The analysis was conducted by researchers from the University of Pittsburgh Graduate School of Public Health.

Not knowing the correct number of deaths makes it more difficult to align resources, according to the researchers.

Cause-of-death codes are assigned by the National Center for Health Statistics (NCHS) using information reported by the coroner or medical examiner completing the death certificate. Drug-specific overdose deaths are identified by the contributory causes of death, which are categorized as "T codes" and are assigned based on the specific drugs recorded by the coroner or medical examiner completing the death certificate. A code of T50.9 means "other and unspecified drugs, medicaments and biological substances."

Researchers extracted death data by state from the NCHS. They grouped overdose deaths into opioid-related, non–opioid-related, and unspecified codes, and calculated the change in percentage of overdose deaths that fell into each category by state. They then extrapolated how many of the unspecified overdose deaths were likely opioid-related.

From 1999 to 2015, a total of 438,607 people died from unintentional drug overdoses. Opioid-related overdose deaths rose 401% (from 5868 to 29,383), non–opioid-related overdose deaths rose 150% (from 3005 to 7505), and unspecified overdose deaths rose 220% (from 2255 to 29,383).

Most opioid-related overdose deaths were coded as X42, and most unspecified overdose deaths were coded as X44. Of 438,607 overdose deaths, 255,527 (58%) were coded as opioid-related, 85,608 (20%) were coded as non–opioid-related, and 97,159 (22%) were coded as unspecified.

Opioid pain relievers (41.5%) were the most commonly reported opioid causing overdose deaths, followed by heroin (25.4%), methadone (20.3%), other and unspecified narcotics (14.4%), synthetic opioids other than methadone (14.2%), and opium (0.01%).

In 5 states (Alabama, Indiana, Louisiana, Mississippi, and Pennsylvania), more than 35% of unintentional overdose deaths were coded as unspecified. The reallocation resulted in classifying more than 70,000 unspecified overdose deaths as potential additional opioid-related overdose deaths.

After reallocation, the number of opioid-related overdose deaths more than doubled in Alabama, Indiana, Louisiana, Mississippi, and Pennsylvania. California, Florida, and Pennsylvania each added more than 5000 opioid-related overdose deaths through reallocation, bringing their totals to 30,813, 25,144, and 20,521, respectively.

"Multiple organizations have advocated for more accurate drug reporting on death certificates," said Jeanine M. Buchanich, PhD, research associate professor in Pitt Public Health's Department of Biostatistics, in a statement. "But coroners are less likely to be physicians and do not necessarily have medical training useful for completing drug information for death certificates based on toxicology reports. And states with a decentralized or hybrid system are likely to have less standardization, leading to greater variation in reporting accuracy."

The variability among states not reporting specific drugs ranged from fewer than 10 unspecified overdose deaths in Vermont to 11,152 in Pennsylvania.

Several states have made efforts to improve reporting, the study noted. In Kentucky, opioid-related drug codes increased 43% from 1999 through 2015, and unspecified drug reporting fell 28%.

The study said several assumptions were made, primarily that the proportion of known opioid-related deaths would be the same for those that were unspecified by state by year. Future research should more fully evaluate these assumptions and also examine other factors, such as potential biases, that could lead coroners and medical examiners to use an unspecified versus specific drug code on death certificates, Buchanich said.

Buchanich JM, Balmert LC, Williams KE, Burke DS. The effect of incomplete death certificates on estimates of unintentional opioid-related overdose deaths in the United States, 1999-2015 [published online June 27, 2018]. Public Health Rep. doi: 10.1177/0033354918774330.
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