Population served extracted from individual hospital CQC reports Abbreviations: Principal Investigator (PI); RN = Research Nurse (RN); Study administrator (SA)

Contributors : The study was designed by TMR, who also ran the study data gathering and management of the sample and results. Specialist biochemical and genetic analyses were performed by KT and KB. Data were analysed by TMR and ASW, and they wrote the study manuscript. The final manuscript as submitted was approved by all the authors.

Funding : This work was supported by an investigator grant from Sanofi Genzyme Therapeutics, Oxford. Research nurses were funded by the National Institute for Health Research.

Competing interests : TMR is currently in receipt of project grants from Genzyme Therapeutics, Oxford, UK (now Sanofi Genzyme, Oxford, UK); Shire Pharmaceuticals, Basingstoke, UK, now Takeda Pharmaceutical Ltd; and Synageva BioPharma, Watford, UK (now Alexion Pharma UK, Uxbridge, UK).

Patient consent for publication : Not required.

Ethics approval : The project received ethics approval from the National Research Ethics Service Committee East Midlands - Northampton (UK Integrated Research Application System project number 158121; 14/EM/1153; 14/10/2014). It was included in the National Institute for Health Research portfolio (UKCRN ID: 17588) and transferred to Health Research Authority on 15 June 2016.