Albuminuria and the emergence of vascular problems in people with Type 2 Diabetes

The role of the kidneys is to filter out what the body doesn’t need while keeping in what it does need. When a person has kidney disease, their kidneys stop carrying out these functions correctly. It is estimated that around 7.2 million people in the UK have chronic kidney disease (CKD), which is defined as having kidney disease for at least three months.

Doctors use two tests to diagnose CKD. The first of these is the eGFR (estimated glomerular filtration rate), which measures how well kidneys are filtering out waste from the blood. These test results break CKD down into five stages, from Stage 1 being the least severe to Stage 5 being the most severe.

The second test doctors use is the uACR (urine albumin-creatinine ratio) that measures how well the kidneys are keeping albumin (a type of protein) in the blood instead of letting it pass into the urine. If a person has too much albumin in their urine, they have albuminuria. The combination of the two tests determines how damaged the kidneys are and the patient’s level of risk.

One of the biggest risk factors for developing CKD is Type 2 Diabetes (T2DM). This is because T2DM can cause high blood sugar levels when not managed correctly, which can damage blood vessels and the small filtering units, called nephrons, in the kidneys. In addition to CKD, T2DM also increases the risk of a range of macro-vascular (large blood vessels) and micro-vascular (small blood vessels) problems. Little is known about the association between varying degrees of albuminuria and the emergence of vascular problems in people with T2DM.

The first aim of the study was to understand the association between varying degrees of albuminuria and the development of vascular multi-morbidities in people with T2DM who have developed stage 3a CKD (CKD3a). The second aim was to quantify the prescription of medications beneficial in delaying CKD progression and reducing the risk of co-morbid disorders.

We extracted data from the Discover London SDE database. Discover London SDE is a de-identified database of healthcare records for 2.8 million people registered to a GP practice in Northwest London. We used the Discover London SDE to identify all patients with a diagnosis of T2DM prior to 2015 who went on to develop stage 3a CKD during 2015. Patients were then put into three groups (CKD3aA1, CKD3aA2, and CKD3aA3) based on their degree of albuminuria, with CKD3aA3 being the group with the most severe albuminuria.

We identified vascular complications of T2DM that were present during the baseline year of 2015 and that emerged over six years from 2016 to 2021. We used statistical tests to assess whether there were any differences between the three groups in the rates of co-morbid disorders at the start of the study period in 2015 and at the end of the follow-up period in 2021.

While 1,028 patients met the study criteria of having been diagnosed with T2DM prior to 2015 and developing stage 3a CKD during 2015, only 471 (46%) of these patients had a uACR test during 2015.

Diabetic retinopathy, hypertension, and Ischaemic Heart Disease (IHD) were the three most common co-morbidities at baseline in 2015, but there was no association between the degree of albuminuria and the rate of these conditions. An increase in hypertension, retinopathy, IHD, and vascular disease from baseline compared to study end point in 2021 was observed for all three groups.

A higher percentage of patients with the most severe albuminuria, CKD3aA3, had eye complications by the end of the study than did patients with the least severe albuminuria, CKD3aA1. They also had a higher rate of hypertension and heart failure than patients with CKD3aA2 by the end of the study.

Only 40% of patients were prescribed a medication that can slow CKD progression and lower the risk of developing a co-morbid disorder in the last six months of the study.

This study uses real world data to show that people with T2DM already have a range of vascular co-morbidities around the time of their CKD diagnosis, with the percentage of patients facing complications increasing over the six-year study period. The development of some complications was associated with the degree of albuminuria at the start of the study period. This demonstrates the importance of conducting timely uACR tests to properly assess risk and enable the use of beneficial medications. This is particularly true given that within our study cohort less than half of T2DM patients had a uACR test conducted during the year they received a CKD diagnosis.