Does the 340B program improve quality of care?

According to a paper by Smith et al. 2023, the answer is ‘no’. The authors use data from
AHRQ’s Healthcare Cost and Utilization Project (HCUP) State Inpatient Data, Hospital Cost Reporting Information System Data, Office of Pharmacy Affairs Information System Data, and American Hospital Association Annual Survey for 15 states between 2008 to 2014. The authors compare hospitals just above vs. below the disproportionate share hospital (DSH) threshold to qualify for 340B drug pricing program. They find that:

We did not find discontinuities in inpatient care quality across the Program eligibility threshold for Medicaid and uninsured patients; specifically, on all-cause mortality (beta = −0.04 percentage points, 95% CI: −0.16, 0.08), 30-day readmission rates (beta = −0.16 percentage points, 95% CI: −0.81, 0.5), or other measures. 

Interestingly, the authors did find that there was some evidence of quality improvement among insured non-Medicaid patients. Counterintuitively, those patients that the 340B program was supposed to help–the uninsured and Medicaid patients–do not seem to be benefiting from the program.