Study design and setting
Data for this observational study were obtained from electronic medical records from five primary care practices in the center of the Netherlands. Considering this is an observational study using pseudonymized routine care data and that the patients had consented before on using their routine care data for research purposes, approval from the Medical Ethical Committee was not obligated.
All patients within the five primary care practices with an International Classification of Primary Care (ICPC) code for T2DM (T90.02) and/or COPD (R95) were included. In august 2019 data were extracted from the electronic medical records (over the period January 1st,2017 until July 26th, 2019).
For patients with T2DM and COPD the treatment setting was determined: treatment in primary care, treatment in secondary care or no care at all. For T2DM and COPD patients who were treated in secondary care the reason for referral was extracted and compared with the RTA for T2DM and COPD (see Additional file 1). The RTA for T2DM provides clear criteria when to refer a patient. For COPD patients the treatment setting was determined differently. When COPD patients treated in secondary care did not meet the criteria for treatment in primary care, they were classified as correctly treated in secondary care. For T2DM and COPD patients treated in secondary care it was assessed if a specialist report was received during the study period. If there was no specialist letter, routine care data from the electronic medical records were used.
Referral and follow up of healthcare in secondary care
In the Netherlands most patients with T2DM and COPD are treated in primary care . National and regional agreements have been developed to define the indications for referral of patients from primary to secondary care. When referring a patient to the hospital the GP sends all relevant patient- and disease information to the specialist in secondary care. This referral is accompanied by a detailed clinical question and a suggestion for the follow-up care. During the treatment in secondary care the treating specialist yearly sends a report to the GP to inform the GP about the treatment provided in secondary care.
Type 2 diabetes specific characteristics
Data were extracted from the electronic medical records on patient characteristics (age and sex), disease duration, systolic blood pressure, glycosylated hemoglobin (HbA1c), LDL-cholesterol, estimated glomerular filtration rate, albumin/creatinine ratio in urine, body mass index, diabetic complications, glucose lowering medication, statin use and lifestyle advise.
Disease duration was defined in years and calculated as the duration until 2018. Data on the microvascular complications retinopathy, nephropathy and neuropathy were collected. Retinopathy was defined as retinopathy seen with fundoscopy in one or two eyes. Nephropathy was defined as an eGFR lower than 60 and/or an albumin/creatinine ratio in urine from 3.0 or higher. For the estimated glomerular filtration rate the Chronic Kidney Disease Epidemiology Collaboration formula was used. Neuropathy was defined as a decreased sensation of the monofilament on one or both feet and/or a score from two or higher on the modified Sims classification. Data on the macrovascular complications angina pectoris (ICPC K74), myocardial infarction (ICPC K75), ischemic heart disease without angina (ICPC K76), transient cerebral incident (ICPC K89), cerebral infarction (ICPC K90.03) and intermittent claudication (ICPC K92.1) were extracted from the electronic medical records. Both micro- and macrovascular complications were defined as the presence of one or more complications per category.
COPD specific characteristics
Patient characteristics (age and sex), systolic blood pressure, use of inhalation medication, spirometry results, smoking status, body mass index, Clinical COPD Questionnaire (CCQ) and Medical Research Council (MRC) dyspnea scale scores were extracted from the electronic medical records.. The CCQ is a questionnaire used to establish the health status of COPD patients. It consists of three domains: symptom status (4 items), functional status (4 items) and mental status (2 items). The outcome is a sum of all domains ranging from zero to six, with a higher outcome indicating a lower health status . The MRC dyspnea scale is a scale to establish how much dyspnea patients experience, it ranges from one to five, with a higher score indicating more dyspnea . Spirometry results are represented by the percentage of expected on the forced expiratory volume in one second (FEV1%pred).
Chronic disease related characteristics
Polypharmacy was defined as the prescription of five or more chronic medications per patient . Frailty of patients was determined according to the Frailty Index . Patients were considered frail when the Frailty Index was higher than 0.2. Data on polypharmacy and frailty were only available for patients 60 years and older. Multimorbidity was defined as the presence of two or more chronic conditions selected from a list from the Netherlands institute for health services research (NIVEL) .
Descriptive statistics were performed using IBM SPSS Statistics (version 25.0, IBM Corporation, Armonk, New York, USA). If more than one measure of the same determinant was present in the study period, the average of the measures was calculated and used for further analysis. Difference in continues characteristics between patients treated in primary care and those treated in secondary care were determined by using the Independent T-test or Mann–Whitney U test when appropriate. Differences in categorical variables were determined by using the χ2-test or Fisher exact test when appropriate. A p-value of less than 0.05 was considered to be statistically significant.