Lipid testing trends before and after hospitalization for myocardial infarction among adults in the U.S., 2008–2019
Authors: Levintow S N , Reading S R , Noshad S , Mayer S , Wiener C , Eledath B , Palagashvili T , Brookhart M A 
Published: October 2021

Abstract

Background
Routine monitoring of low-density lipoprotein cholesterol (LDL-C) identifies patients who are candidates for initiation of lipid-lowering therapies (LLT), assesses adherence and response, and measures clinical indications for modifications to treatment. This study investigated LDL-C testing trends among patients hospitalized for incident myocardial infarction (MI), a population at high risk of future atherosclerotic cardiovascular disease (ASCVD) events who may benefit from additional LLT.

Purpose
Our objective was to estimate rates of LDL-C testing before and after MI hospitalization, hypothesizing that testing rates would increase following MI.

Methods
Using claims data from a large population with Medicare supplemental or commercial insurance, we identified U.S. adults aged ≥20 years discharged from a MI hospitalization. Patients qualified for the study cohort if their first MI hospitalization occurred during 1/1/2008–3/31/2019, with one year of continuous enrolment in insurance leading up to the hospitalization. Patients were required to be discharged alive to the community (excluded if died or transferred to another facility). LDL-C testing was assessed in the year before admission (pre-MI) and for up to one year after discharge (post-MI), with censoring due to insurance plan disenrollment. To evaluate changes in LDL-C testing, we fit an overdispersed Poisson model to the time-series of pre-MI rates and extrapolated the model to the post-MI period, accounting for person-time and seasonality. We predicted the LDL-C testing rates if no MI occurred (i.e., based only on pre-MI testing trends) and estimated rate differences with 95% confidence intervals (contrasting observed vs. model-predicted rates).

Results
A total of 389,367 patients were hospitalized for their first MI during the study period with 60% aged &lt;65 years, 64% were male, and 51% filled a statin prescription after discharge (half being high-intensity statins). In the year pre-MI, 25% had a history of diabetes mellitus, 35% used statins, and 4% used ezetimibe. In the year post-MI, only 52% had an LDL-C test. Mean observed rates (tests per 1,000 patients per month) in the pre- and post-MI periods were 51.9 (95% CI: 51.7, 52.1) and 84.4 (95% CI: 84.1, 84.6), respectively. Across the 12 months post-MI, observed rates were higher than model-predicted rates, with the magnitude of rate differences changing over time (Figure). The observed testing rate peaked two months post-MI (rate difference: 65.7, 95% CI: 64.6, 66.7).

Conclusions
Our findings indicate that LDL-C testing rates increased following a MI hospitalization and stayed elevated throughout the following year. Despite this increase, overall rates remained low, with only one in two patients receiving an LDL-C test in the year after MI. These results highlight a potential gap in care, particularly given the importance of LDL-C monitoring for this population to reduce risk of future ASCVD events.

Funding Acknowledgement
Type of funding sources: Private company. Main funding source(s): This study was funded by Amgen, Inc. Several authors are employees and own stock in Amgen.