Loop diuretics are one of the most commonly prescribed medications in primary care. However, there are few indications for loop diuretics other than the treatment of venous congestion in patients with heart failure (HF).
A pilot study at a single General Practice in East Yorkshire found that of 94 patients who were taking loop diuretic without a diagnostic code for HF in their electronic record, 13% were diagnosed with HF, and 25% died or were hospitalised with HF during 2 years’ follow up. It is possible that a proportion of these patients had undiagnosed HF as the cause of their symptoms. Furthermore, use of loop diuretics may mask symptoms of congestion without treating the underlying disease; thus delaying diagnosis and worsening outcome. Whether these results are generalisable is unknown.
Our project will use data from the CPRD to investigate the link between loop diuretic prescription and HF-related events in two separate cohort comparisons. Firstly (analysis A), between patients prescribed loop diuretic without a diagnostic code for HF in their electronic record (study population) and patients with a diagnostic code for HF (control group 1), propensity matched for age, sex and co-morbidities. Secondly (analysis B), between the study population and patients with risk factors for HF propensity matched for age, sex and co-morbidities (control group 2). Using independent samples T-test and hazard regressions, we will compare the number of consultations with HF symptoms, the number of new HF diagnoses (analysis B), the number of cause specific hospitalisations and the number of cause specific deaths. We will also compare the time to each event using Cox regression adjusted for important co-variables such as age. Hospital Episode Statistics Admitted Patient Care (HES APC) will be used to determine hospitalisations and Office of National Statistics death registration data will be used to determine deaths.
All outcomes assessed at yearly intervals over a five year period.
Primary Outcomes
Number of first hospitalisations with heart failure in any diagnostic position; number of recurrent hospitalisations with heart failure; number of all-cause deaths; time to first hospitalisation with heart failure in any diagnostic position; time to all-cause death; number of new heart failure diagnoses (analysis B); time to heart failure diagnosis (analysis B).
Secondary Outcomes
Number of consultations with breathlessness, fatigue, ankle swelling, or any combination of symptoms; number of patients undergoing natriuretic peptide testing; number of patients undergoing echocardiography; number of patients referred to outpatient cardiology services; number of new prescriptions of loop diuretics (amongst patients in control group 2); number of cause-specific hospitalisations; time to any hospitalisation; number of cardiovascular deaths; time to cardiovascular death.
Joe Cuthbert - Chief Investigator - Hull York Medical School
Joe Cuthbert - Corresponding Applicant - Hull York Medical School
Ahmet Fuat - Collaborator - Durham University
Andrew Clark - Collaborator - University Of Hull
Ireneous Soyiri - Collaborator - University Of Hull
John Turgoose - Collaborator - Hull York Medical School
Judith Cohen - Collaborator - University Of Hull
HES Admitted Patient Care;ONS Death Registration Data