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Outcomes for Surgical Procedures Funded by the English Health Service but Carried out in Public vs. Independent Hospitals: a Database Study

Leads: Prof Richard Lilford, Dr Katharine Reeves (Meths), Mr Aneel Bhangu (Long-term Conditions), Prof Kamlesh Khunti (ARC EM)

Public Contributors linked to the ARC WM Research Methods theme will work with the project leads to maximise impact of this study.

Dates: October 2019 - January 2021


The NHS contracts work to private sector healthcare companies which we term Independent Sector Healthcare Providers (ISHPs). This has increased over time and represented 7.5% of total NHS expenditure by 2015/16.

Policy and Practice Partners:

Independent hospitals, commissioners of services, primary care organisations.

Co-Funding Partners:


Aims and Objectives:

To compare the outcomes of NHS patients undergoing elective surgery operations in NHS hospitals compared to those at Independent Sector Healthcare Providers (ISHPs).


Admitted Patient Care data from the England-wide Hospital Episode Statistics (HES) database was used for this analysis. The study included all elective admissions for one of a list of 18 common surgical procedures, occurring between 2006 and 2019. The primary outcomes studied were: length of stay (operation date to discharge) and 28-day emergency readmissions. Secondary outcomes included emergency transfers and deaths. Outcomes were compared for each operation type, adjusted for age, ethnicity, comorbidity, gender and deprivation (based on the neighbourhood in which the patient lives) by means of propensity score matching followed by survival analysis. Our analysis took account of competing risks, such as death after discharge and readmission.

Main Results:

Across all operation types studied we found length of stay was significantly longer for patients treated in NHS hospitals compared to Independent Sector Healthcare Providers (ISHPs) (significance assessed at 95% level). For all operation types post discharge readmissions were lower for ISHP patients than for patients treated in NHS hospitals. The effect was large, amounting to a 70% reduction for some operations. The effects were the same across for-profit and not-for-profit ISHPs. The effects were also the same over the 15 years of observations and across different risk strata. Deaths were very rare, and did not differ significantly, except for one operation, where again better outcomes were seen in ISHPs.


Elective surgery in an ISHP is associated with shorter lengths of stay and lower readmission rates than treatment in NHS hospitals. This finding is consistent across 18 disparate operation types. The data were matched on observable covariates but we cannot exclude selection bias due to unobserved confounders. Compared to what may have been concluded had the results favoured surgery in NHS hospitals, these findings provide a measure of reassurance regarding the safety and quality of elective surgery in ISHPs.

Implications for Implementation:

This data suggests that the quality of care provided by the independent sector hospitals is no worse, and arguably better, than that provided in NHS hospitals for NHS funded elective surgical procedures. This suggests that patients should retain the option to have surgery in independent hospitals.


Crothers H, Liaqat A, Reeves K, Watson SI, Gallier S, Khunti K, Bird P, Lilford R. Outcomes for surgical procedures funded by the English health service but carried out in public versus independent hospitals: a database study. BMJ Qual Saf. 2021 Sep 7:bmjqs-2021-013522. 10.1136/bmjqs-2021-013522.