Primary Care (incident)

In the Clinical Practice Research Datalink (CPRD, primary care data) we ascertained diabetes cases by searching for Read terms related to diagnosis.

Read code	Read term	CALIBER category
C108.12	Type 1 diabetes mellitus	Type I diabetes mellitus
C108.13	Type I diabetes mellitus	Type I diabetes mellitus
C108011	Type I diabetes mellitus with renal complications	Type I diabetes mellitus
C108012	Type 1 diabetes mellitus with renal complications	Type I diabetes mellitus
C108211	Type I diabetes mellitus with neurological complications	Type I diabetes mellitus
C108212	Type 1 diabetes mellitus with neurological complications	Type I diabetes mellitus
C108411	Unstable type I diabetes mellitus	Type I diabetes mellitus
C108412	Unstable type 1 diabetes mellitus	Type I diabetes mellitus
C108511	Type I diabetes mellitus with ulcer	Type I diabetes mellitus
C108512	Type 1 diabetes mellitus with ulcer	Type I diabetes mellitus
C108711	Type I diabetes mellitus with retinopathy	Type I diabetes mellitus
C108712	Type 1 diabetes mellitus with retinopathy	Type I diabetes mellitus
C108811	Type I diabetes mellitus - poor control	Type I diabetes mellitus
C108812	Type 1 diabetes mellitus - poor control	Type I diabetes mellitus
C108911	Type I diabetes mellitus maturity onset	Type I diabetes mellitus
C108912	Type 1 diabetes mellitus maturity onset	Type I diabetes mellitus
C108A11	Type I diabetes mellitus without complication	Type I diabetes mellitus
C108D11	Type I diabetes mellitus with nephropathy	Type I diabetes mellitus
C108E11	Type I diabetes mellitus with hypoglycaemic coma	Type I diabetes mellitus
C108E12	Type 1 diabetes mellitus with hypoglycaemic coma	Type I diabetes mellitus
C108F11	Type I diabetes mellitus with diabetic cataract	Type I diabetes mellitus
C108H11	Type I diabetes mellitus with arthropathy	Type I diabetes mellitus
C108J11	Type I diabetes mellitus with neuropathic arthropathy	Type I diabetes mellitus
C108J12	Type 1 diabetes mellitus with neuropathic arthropathy	Type I diabetes mellitus
C10E.00	Type 1 diabetes mellitus	Type I diabetes mellitus
C10E.11	Type I diabetes mellitus	Type I diabetes mellitus
C10E000	Type 1 diabetes mellitus with renal complications	Type I diabetes mellitus
C10E100	Type 1 diabetes mellitus with ophthalmic complications	Type I diabetes mellitus
C10E200	Type 1 diabetes mellitus with neurological complications	Type I diabetes mellitus
C10E300	Type 1 diabetes mellitus with multiple complications	Type I diabetes mellitus
C10E311	Type I diabetes mellitus with multiple complications	Type I diabetes mellitus
C10E400	Unstable type 1 diabetes mellitus	Type I diabetes mellitus
C10E411	Unstable type I diabetes mellitus	Type I diabetes mellitus
C10E500	Type 1 diabetes mellitus with ulcer	Type I diabetes mellitus
C10E511	Type I diabetes mellitus with ulcer	Type I diabetes mellitus
C10E600	Type 1 diabetes mellitus with gangrene	Type I diabetes mellitus
C10E700	Type 1 diabetes mellitus with retinopathy	Type I diabetes mellitus
C10E711	Type I diabetes mellitus with retinopathy	Type I diabetes mellitus
C10E800	Type 1 diabetes mellitus - poor control	Type I diabetes mellitus
C10E900	Type 1 diabetes mellitus maturity onset	Type I diabetes mellitus
C10E911	Type I diabetes mellitus maturity onset	Type I diabetes mellitus
C10EA00	Type 1 diabetes mellitus without complication	Type I diabetes mellitus
C10EA11	Type I diabetes mellitus without complication	Type I diabetes mellitus
C10EB00	Type 1 diabetes mellitus with mononeuropathy	Type I diabetes mellitus
C10EC00	Type 1 diabetes mellitus with polyneuropathy	Type I diabetes mellitus
C10EC11	Type I diabetes mellitus with polyneuropathy	Type I diabetes mellitus
C10ED00	Type 1 diabetes mellitus with nephropathy	Type I diabetes mellitus
C10EE00	Type 1 diabetes mellitus with hypoglycaemic coma	Type I diabetes mellitus
C10EF00	Type 1 diabetes mellitus with diabetic cataract	Type I diabetes mellitus
C10EG00	Type 1 diabetes mellitus with peripheral angiopathy	Type I diabetes mellitus
C10EH00	Type 1 diabetes mellitus with arthropathy	Type I diabetes mellitus
C10EJ00	Type 1 diabetes mellitus with neuropathic arthropathy	Type I diabetes mellitus
C10EK00	Type 1 diabetes mellitus with persistent proteinuria	Type I diabetes mellitus
C10EL00	Type 1 diabetes mellitus with persistent microalbuminuria	Type I diabetes mellitus
C10EM00	Type 1 diabetes mellitus with ketoacidosis	Type I diabetes mellitus
C10EM11	Type I diabetes mellitus with ketoacidosis	Type I diabetes mellitus
C10EN00	Type 1 diabetes mellitus with ketoacidotic coma	Type I diabetes mellitus
C10EN11	Type I diabetes mellitus with ketoacidotic coma	Type I diabetes mellitus
C10EP00	Type 1 diabetes mellitus with exudative maculopathy	Type I diabetes mellitus
C10EP11	Type I diabetes mellitus with exudative maculopathy	Type I diabetes mellitus
C10EQ00	Type 1 diabetes mellitus with gastroparesis	Type I diabetes mellitus
C109.12	Type 2 diabetes mellitus	Type II diabetes mellitus
C109.13	Type II diabetes mellitus	Type II diabetes mellitus
C109011	Type II diabetes mellitus with renal complications	Type II diabetes mellitus
C109012	Type 2 diabetes mellitus with renal complications	Type II diabetes mellitus
C109111	Type II diabetes mellitus with ophthalmic complications	Type II diabetes mellitus
C109112	Type 2 diabetes mellitus with ophthalmic complications	Type II diabetes mellitus
C109211	Type II diabetes mellitus with neurological complications	Type II diabetes mellitus
C109212	Type 2 diabetes mellitus with neurological complications	Type II diabetes mellitus
C109411	Type II diabetes mellitus with ulcer	Type II diabetes mellitus
C109412	Type 2 diabetes mellitus with ulcer	Type II diabetes mellitus
C109511	Type II diabetes mellitus with gangrene	Type II diabetes mellitus
C109512	Type 2 diabetes mellitus with gangrene	Type II diabetes mellitus
C109611	Type II diabetes mellitus with retinopathy	Type II diabetes mellitus
C109612	Type 2 diabetes mellitus with retinopathy	Type II diabetes mellitus
C109711	Type II diabetes mellitus - poor control	Type II diabetes mellitus
C109712	Type 2 diabetes mellitus - poor control	Type II diabetes mellitus
C109A11	Type II diabetes mellitus with mononeuropathy	Type II diabetes mellitus
C109B11	Type II diabetes mellitus with polyneuropathy	Type II diabetes mellitus
C109C11	Type II diabetes mellitus with nephropathy	Type II diabetes mellitus
C109C12	Type 2 diabetes mellitus with nephropathy	Type II diabetes mellitus
C109D11	Type II diabetes mellitus with hypoglycaemic coma	Type II diabetes mellitus
C109D12	Type 2 diabetes mellitus with hypoglycaemic coma	Type II diabetes mellitus
C109E11	Type II diabetes mellitus with diabetic cataract	Type II diabetes mellitus
C109E12	Type 2 diabetes mellitus with diabetic cataract	Type II diabetes mellitus
C109F11	Type II diabetes mellitus with peripheral angiopathy	Type II diabetes mellitus
C109F12	Type 2 diabetes mellitus with peripheral angiopathy	Type II diabetes mellitus
C109G11	Type II diabetes mellitus with arthropathy	Type II diabetes mellitus
C109G12	Type 2 diabetes mellitus with arthropathy	Type II diabetes mellitus
C109H11	Type II diabetes mellitus with neuropathic arthropathy	Type II diabetes mellitus
C109H12	Type 2 diabetes mellitus with neuropathic arthropathy	Type II diabetes mellitus
C109J00	Insulin treated Type 2 diabetes mellitus	Type II diabetes mellitus
C109J12	Insulin treated Type II diabetes mellitus	Type II diabetes mellitus
C109K00	Hyperosmolar non-ketotic state in type 2 diabetes mellitus	Type II diabetes mellitus
C10F.00	Type 2 diabetes mellitus	Type II diabetes mellitus
C10F.11	Type II diabetes mellitus	Type II diabetes mellitus
C10F000	Type 2 diabetes mellitus with renal complications	Type II diabetes mellitus
C10F011	Type II diabetes mellitus with renal complications	Type II diabetes mellitus
C10F100	Type 2 diabetes mellitus with ophthalmic complications	Type II diabetes mellitus
C10F200	Type 2 diabetes mellitus with neurological complications	Type II diabetes mellitus
C10F211	Type II diabetes mellitus with neurological complications	Type II diabetes mellitus
C10F300	Type 2 diabetes mellitus with multiple complications	Type II diabetes mellitus
C10F311	Type II diabetes mellitus with multiple complications	Type II diabetes mellitus
C10F400	Type 2 diabetes mellitus with ulcer	Type II diabetes mellitus
C10F411	Type II diabetes mellitus with ulcer	Type II diabetes mellitus
C10F500	Type 2 diabetes mellitus with gangrene	Type II diabetes mellitus
C10F600	Type 2 diabetes mellitus with retinopathy	Type II diabetes mellitus
C10F611	Type II diabetes mellitus with retinopathy	Type II diabetes mellitus
C10F700	Type 2 diabetes mellitus - poor control	Type II diabetes mellitus
C10F711	Type II diabetes mellitus - poor control	Type II diabetes mellitus
C10F900	Type 2 diabetes mellitus without complication	Type II diabetes mellitus
C10F911	Type II diabetes mellitus without complication	Type II diabetes mellitus
C10FA00	Type 2 diabetes mellitus with mononeuropathy	Type II diabetes mellitus
C10FA11	Type II diabetes mellitus with mononeuropathy	Type II diabetes mellitus
C10FB00	Type 2 diabetes mellitus with polyneuropathy	Type II diabetes mellitus
C10FB11	Type II diabetes mellitus with polyneuropathy	Type II diabetes mellitus
C10FC00	Type 2 diabetes mellitus with nephropathy	Type II diabetes mellitus
C10FD00	Type 2 diabetes mellitus with hypoglycaemic coma	Type II diabetes mellitus
C10FD11	Type II diabetes mellitus with hypoglycaemic coma	Type II diabetes mellitus
C10FE00	Type 2 diabetes mellitus with diabetic cataract	Type II diabetes mellitus
C10FE11	Type II diabetes mellitus with diabetic cataract	Type II diabetes mellitus
C10FF00	Type 2 diabetes mellitus with peripheral angiopathy	Type II diabetes mellitus
C10FG00	Type 2 diabetes mellitus with arthropathy	Type II diabetes mellitus
C10FH00	Type 2 diabetes mellitus with neuropathic arthropathy	Type II diabetes mellitus
C10FJ00	Insulin treated Type 2 diabetes mellitus	Type II diabetes mellitus
C10FJ11	Insulin treated Type II diabetes mellitus	Type II diabetes mellitus
C10FK00	Hyperosmolar non-ketotic state in type 2 diabetes mellitus	Type II diabetes mellitus
C10FL00	Type 2 diabetes mellitus with persistent proteinuria	Type II diabetes mellitus
C10FL11	Type II diabetes mellitus with persistent proteinuria	Type II diabetes mellitus
C10FM00	Type 2 diabetes mellitus with persistent microalbuminuria	Type II diabetes mellitus
C10FM11	Type II diabetes mellitus with persistent microalbuminuria	Type II diabetes mellitus
C10FN00	Type 2 diabetes mellitus with ketoacidosis	Type II diabetes mellitus
C10FP00	Type 2 diabetes mellitus with ketoacidotic coma	Type II diabetes mellitus
C10FQ00	Type 2 diabetes mellitus with exudative maculopathy	Type II diabetes mellitus
C10FR00	Type 2 diabetes mellitus with gastroparesis	Type II diabetes mellitus

Primary Care (prevalent)

Read code	Read term	CALIBER category
1434.00	H/O: diabetes mellitus	H/O diabetes
14F4.00	H/O: Admission in last year for diabetes foot problem	H/O diabetes
14P3.00	H/O: insulin therapy	H/O diabetes
2126300	Diabetes resolved	H/O diabetes
212H.00	Diabetes resolved	H/O diabetes
9OL9.00	Diabetes monitoring deleted	H/O diabetes

Read terms are hierarhically organized in top-level chapters i.e. chapter G....00 is related to Circulatory System Diseases and sub-headings i.e. heading G2...00 is related to Hypertensive Heart Disease while G3...00 is related to Ischaemic Heart Disease.

Secondary Care (incident and prevalent)

In Hospital Episode Statistics (HES, hospital admission data) we used ICD-10 codes (see below) for Transcient Ischaemic Attack diagnosis when marked as the primary diagnosis i.e. the main condition treated or investigated during the relevant episode of healthcare. We used the date of admission to hospital as the date of the event.

ICD-10 code	ICD-10 term	CALIBER category
E10	Insulin-dependent diabetes mellitus	Insulin dependent diabetes
E11	Non-insulin-dependent diabetes mellitus	Non insulin dependent diabetes
E12	Malnutrition-related diabetes mellitus	Secondary diabetes
O242	Diabetes mellitus in pregnancy: Pre-existing malnutrition-related diabetes mellitus	Secondary diabetes

Not applicable.

Combining evidence across sources to define and date phenotypes

The aim of this algorithm is to identify patients with type 2 diabetes. The majority of diabetic patients in this cohort have type 2 diabetes, and we are not aiming to identify all patients with type 1 diabetes (this algorithm would not be suitable for a study focusing on type I diabetes). Our algorithm does not use any information after study entry to classify patients, in order to reduce immortal time bias. However this bias is not eliminated completely because specific type 1 or type 2 codes may have been entered retrospectively only for patients who survived.

Our algorithm leaves many patients with an unclassified type of diabetes. However, rather than using a more complex algorithm, we carried out sensitivity analyses with different definitions (e.g. the type 2 definition or any diabetes).

Pseudocode implementation

IF there is at least one record for code for type 2 diabetes 
and no record for type 1 diabetes then classify the patient as type 2 diabetes

ELSE if there is at least one record for code for type I diabetes 
and no record for type 2 diabetes then classify the patient as type 1 diabetes

ELSE if there is at least one record of type 1 diabetes 
and type 2 diabetes then classify as diabetes of uncertain type

ELSE if there are no diabdiag_gprd records for this patient:

If there is at least one record for NIDDM and no record for IDDM 
    then classify the patient as type 2 diabetes

ELSE there is at least one record for IDDM 
    and no record for NIDDM 
    then classify the patient as type 1 diabetes

ELSE if there is at least one record of diabetes
    then classify as diabetes of uncertain type

ELSE classify as no diabetes

• Prognosis
• Aetiology

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Steele AJ et al. Machine learning models in electronic health records can outperform conventional survival models for predicting patient mortality in coronary artery disease. PLoS One. 2018 Aug 31;13(8):e0202344. doi: 10.1371/journal.pone.0202344. eCollection 2018. PMID: 30169498


Archangelidi O et al. Clinically recorded heart rate and incidence of 12 coronary, cardiac, cerebrovascular and peripheral arterial diseases in 233,970 men and women: A linked electronic health record study. Eur J Prev Cardiol. 2018 Sep;25(14):1485-1495. doi: 10.1177/2047487318785228. Epub 2018 Jul 2. PMID: 29966429


Koudstaal S et al. Prognostic burden of heart failure recorded in primary care, acute hospital admissions, or both: a population-based linked electronic health record cohort study in 2.1 million people. Eur J Heart Fail. 2017 Sep;19(9):1119-1127. doi: 10.1002/ejhf.709. Epub 2016 Dec 23. PMID: 28008698


Chung SC et al. Time spent at blood pressure target and the risk of death and cardiovascular diseases. PLoS One. 2018 Sep 5;13(9):e0202359. doi: 10.1371/journal.pone.0202359. eCollection 2018. PMID: 30183734


Bell S et al. Association between clinically recorded alcohol consumption and initial presentation of 12 cardiovascular diseases: population based cohort study using linked health records. BMJ. 2017 Mar 22;356:j909. PMID: 28331015


Pasea L et al. Personalising the decision for prolonged dual antiplatelet therapy: development, validation and potential impact of prognostic models for cardiovascular events and bleeding in myocardial infarction survivors. Eur Heart J. 2017 Apr 7;38(14):1048-1055. doi: 10.1093/eurheartj/ehw683. PMID: 28329300


Shah AD et al. Neutrophil Counts and Initial Presentation of 12 Cardiovascular Diseases: A CALIBER Cohort Study. J Am Coll Cardiol. 2017 Mar 7;69(9):1160-1169. doi: 10.1016/j.jacc.2016.12.022. PMID: 28254179


Asaria M et al. Using electronic health records to predict costs and outcomes in stable coronary artery disease. Heart. 2016 May 15;102(10):755-62. doi: 10.1136/heartjnl-2015-308850. Epub 2016 Feb 10. PMID: 26864674


Daskalopoulou M et al. Depression as a Risk Factor for the Initial Presentation of Twelve Cardiac, Cerebrovascular, and Peripheral Arterial Diseases: Data Linkage Study of 1.9 Million Women and Men. PLoS One. 2016 Apr 22;11(4):e0153838. doi: 10.1371/journal.pone.0153838. eCollection 2016. PMID: 27105076


Pujades-Rodriguez M et al. Associations between polymyalgia rheumatica and giant cell arteritis and 12 cardiovascular diseases. Heart. 2016 Mar;102(5):383-9. doi: 10.1136/heartjnl-2015-308514. Epub 2016 Jan 19. PMID: 26786818


Pujades-Rodriguez M et al. Rheumatoid Arthritis and Incidence of Twelve Initial Presentations of Cardiovascular Disease: A Population Record-Linkage Cohort Study in England. PLoS One. 2016 Mar 15;11(3):e0151245. doi: 10.1371/journal.pone.0151245. eCollection 2016. PMID: 26978266


Shah AD et al. Low eosinophil and low lymphocyte counts and the incidence of 12 cardiovascular diseases: a CALIBER cohort study. Open Heart. 2016 Sep 5;3(2):e000477. doi: 10.1136/openhrt-2016-000477. eCollection 2016. PMID: 27621833


Timmis A et al. Prolonged dual antiplatelet therapy in stable coronary disease: comparative observational study of benefits and harms in unselected versus trial populations. BMJ. 2016 Jun 22;353:i3163. PMID: 27334486


Walker S et al. Long-term healthcare use and costs in patients with stable coronary artery disease: a population-based cohort using linked health records (CALIBER). Eur Heart J Qual Care Clin Outcomes. 2016 Jan 20;2(2):125-140. doi: 10.1093/ehjqcco/qcw003. PMID: 27042338


George J et al. How Does Cardiovascular Disease First Present in Women and Men? Incidence of 12 Cardiovascular Diseases in a Contemporary Cohort of 1,937,360 People. Circulation. 2015 Oct 6;132(14):1320-8. doi: 10.1161/CIRCULATIONAHA.114.013797. Epub 2015 Sep 1. PMID: 26330414


Morley KI et al. Defining disease phenotypes using national linked electronic health records: a case study of atrial fibrillation. PLoS One. 2014 Nov 4;9(11):e110900. doi: 10.1371/journal.pone.0110900. eCollection 2014. PMID: 25369203


Pujades-Rodriguez M et al. Heterogeneous associations between smoking and a wide range of initial presentations of cardiovascular disease in 1937360 people in England: lifetime risks and implications for risk prediction. Int J Epidemiol. 2015 Feb;44(1):129-41. doi: 10.1093/ije/dyu218. Epub 2014 Nov 20. PMID: 25416721


Pujades-Rodriguez M et al. Socioeconomic deprivation and the incidence of 12 cardiovascular diseases in 1.9 million women and men: implications for risk prediction and prevention. PLoS One. 2014 Aug 21;9(8):e104671. doi: 10.1371/journal.pone.0104671. eCollection 2014. PMID: 25144739


Rapsomaniki E et al. Blood pressure and incidence of twelve cardiovascular diseases: lifetime risks, healthy life-years lost, and age-specific associations in 1.25 million people. Lancet. 2014 May 31;383(9932):1899-911. doi: 10.1016/S0140-6736(14)60685-1. PMID: 24881994


Shah AD et al. Type 2 diabetes and incidence of cardiovascular diseases: a cohort study in 1.9 million people. Lancet Diabetes Endocrinol. 2015 Feb;3(2):105-13. doi: 10.1016/S2213-8587(14)70219-0. Epub 2014 Nov 11. PMID: 25466521


Rapsomaniki E et al. Prognostic models for stable coronary artery disease based on electronic health record cohort of 102 023 patients. Eur Heart J. 2014 Apr;35(13):844-52. doi: 10.1093/eurheartj/eht533. Epub 2013 Dec 17. PMID: 24353280