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Validation of methods to identify people with idiopathic inflammatory myopathies using hospital episode statistics

Hannah, Jennifer R.; Gordon, Patrick A.; Galloway, James; Rutter, Megan; Peach, Emily J.; Rooney, Michael; Stilwell, Peter; Grainge, Matthew J.; Lanyon, Peter C.; Bythell, Mary; Pearce, Fiona A.


Jennifer R. Hannah

Patrick A. Gordon

James Galloway

Megan Rutter

Emily J. Peach

Michael Rooney

Peter Stilwell

Peter C. Lanyon

Mary Bythell

Clinical Associate Professor


Objective: Hospital episode statistics (HES) are routinely recorded at every hospital admission within the National Health Service (NHS) in England. This study validates diagnostic ICD-10 codes within HES as a method of identifying cases of idiopathic inflammatory myopathies (IIMs). Methods: All inpatient admissions at one NHS Trust between 2010 and 2020 with relevant diagnostic ICD-10 codes were extracted from HES. Hospital databases were used to identify all outpatients with IIM, and electronic care records were reviewed to confirm coding accuracy. Total hospital admissions were calculated from NHS Digital reports. The sensitivity and specificity of each code and code combinations were calculated to develop an optimal algorithm. The optimal algorithm was tested in a sample of admissions at another NHS Trust. Results: Of the 672 individuals identified by HES, 510 were confirmed to have IIM. Overall, the positive predictive value (PPV) was 76% and sensitivity 89%. Combination algorithms achieved PPVs between 89 and 94%. HES can also predict the presence of IIM-associated interstitial lung disease (ILD) with a PPV of 79% and sensitivity of 71%. The optimal algorithm excluded children (except JDM code M33.0), combined M33.0, M33.1, M33.9, M36.0, G72.4, M60.8 and M33.2, and included M60.9 only if it occurred alongside an ILD code (J84.1, J84.9 or J99.1). This produced a PPV of 88.9% and sensitivity of 84.2%. Retesting this algorithm at another NHS Trust confirmed a high PPV (94.4%). Conclusion: IIM ICD-10 code combinations in HES have high PPVs and sensitivities. Algorithms tested in this study could be applied across all NHS Trusts to enable robust and cost-effective whole-population research into the epidemiology of IIM.


Hannah, J., Gordon, P., Galloway, J., Rutter, M., Peach, E., Rooney, M., …Pearce, F. (2022). Validation of methods to identify people with idiopathic inflammatory myopathies using hospital episode statistics. Rheumatology Advances in Practice, 6(3), Article rkac102.

Journal Article Type Article
Acceptance Date Oct 25, 2022
Online Publication Date Dec 14, 2022
Publication Date 2022
Deposit Date Nov 8, 2022
Publicly Available Date Jan 18, 2023
Journal Rheumatology Advances in Practice
Electronic ISSN 2514-1775
Peer Reviewed Peer Reviewed
Volume 6
Issue 3
Article Number rkac102
Public URL
Publisher URL


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