Validating Imputation Procedures to Calculate Corrected Opioid-Involved Overdose Deaths, Marion County, Indiana,...

Understanding the scope of the current opioid epidemic requires accurate counts of the number of opioid-involved drug overdose deaths. Given known errors and limitations in the reporting of these deaths, several studies have used statistical methods to develop estimates of the true number of opioid-involved overdose deaths. This study validates these procedures using a detailed county-level database of linked toxicology and vital records data.

We extracted and linked toxicology and vital records data from Marion County, Indiana (Indianapolis), during a 6-year period (2011-2016). Using toxicology data as a criterion measure, we tested the validity of multiple imputation procedures, including the Ruhm regression-based imputation approach for correcting the number of opioid-involved overdose deaths.

Estimates deviated from true opioid-involved overdose deaths by 3% and increased in accuracy during the study period (2011-2016). For example, in 2016, 231 opioid-involved overdose deaths were noted in the toxicology data, whereas the corresponding imputed estimate was 233 opioid-involved overdose deaths. A simple imputation approach, based on the share of opioid-involved overdose deaths among all drug overdose deaths for which the death certificate specified ≥1 drug, deviated from true opioid-involved overdose deaths by ±5%.

Commonly used imputation procedures produced estimates of the number of opioid-involved overdose deaths that are similar to the true number of opioid-involved overdose deaths obtained from toxicology data. Although future studies should examine whether these results extend beyond the geographic area covered in our data set, our findings support the continued use of these imputation procedures to quantify the extent of the opioid epidemic.