Outcomes for surgical procedures funded by the English health service but carried out in public versus independent hospitals: a database study

Research output: Contribution to journalArticlepeer-review


  • Hannah Crothers
  • Adiba Liaqat
  • Katharine Reeves
  • Suzy Gallier
  • Kamlesh Khunti
  • Paul Bird

Colleges, School and Institutes

External organisations

  • Queen Elizabeth Hospital Birmingham
  • Leicester Diabetes Centre, University Hospitals Leicester


Background The outcomes of elective surgery in public versus Independent Sector Healthcare Providers (ISHPs) are a matter of policy relevance and theoretical interest.

Methods Retrospective study of all National Health Service (NHS) hospitals and ISHPs in England that provided NHS-funded elective surgery. We used data from the England-wide Hospital Episode Statistics to study 18 common surgical procedures performed between 2006 and 2019. In-hospital outcomes included length of stay, emergency transfers to another hospital or death. Posthospital outcomes included readmission or death within 28 days. Outcomes were compared for each operation type by propensity score matching and survival analysis.

Results The data set included 3 203 331 operations in 734 NHS hospitals and 468 259 operations in 274 ISHPs.

In-hospital outcomes: Across all 18 included operation types, length of stay was significantly longer for patients treated in NHS hospitals compared with ISHPs. Effect sizes ranged from a hazard ratio (HR) of 2.15 (95% CI 1.72 to 2.68) for total hip replacement to 1.07 (95% CI 1.05 to 1.09) for wisdom tooth removal; a mean difference of 2.49 and 0.02 days, respectively.

Postdischarge outcomes: Treatment at an ISHP was associated with a lower risk of emergency readmission compared with NHS treatment. HRs ranged from 0.36 (95% CI 0.28 to 0.46) for lumbar decompression to 0.75 (95% CI 0.67 to 0.85) for cholecystectomy; absolute risk differences of 1.5 and 1.3 percentage points. There was no difference in mortality.

Conclusion Elective surgery in an ISHP is associated with shorter lengths of stay and lower readmission rates than treatment in NHS hospitals across 18 operation types. The data were matched on observable covariates, but we cannot exclude selection bias due to unobserved confounders.


Original languageEnglish
JournalBMJ Quality & Safety
Early online date7 Sep 2021
Publication statusE-pub ahead of print - 7 Sep 2021