Chronic kidney disease screening: who should be tested, and how

KDIGO’s first practice point is to test people at risk for CKD using both a urine albumin measurement and an assessment of kidney filtration. The CDC singles out diabetes and high blood pressure as the main risk factors. The UK’s NHS advises regular testing for people with:

• high blood pressure or diabetes;
• a previous acute kidney injury;
• cardiovascular disease;
• other conditions that can affect the kidneys;
• a family history of kidney disease;
• unexplained protein or blood in the urine;
• long-term use of certain medicines, such as lithium, omeprazole or nonsteroidal anti-inflammatory drugs (NSAIDs).

The NHS adds that people of Black or South Asian origin are more likely to develop kidney disease. This list is a guide, not a self-referral form: your doctor weighs your age, history, treatments and previous results. Screening is a form of secondary prevention, finding a problem before it shows; our article on primary, secondary and tertiary prevention explains the distinction.

How France does it

France has made this targeted approach explicit. The Haute Autorité de santé (HAS), the national body that issues clinical guidance, and the Assurance Maladie, the national health insurance, advise against screening everyone. The Assurance Maladie’s guidance for doctors recommends a yearly blood creatinine with eGFR and a urine ACR for people at risk: diabetes, treated or untreated hypertension, atherosclerotic cardiovascular disease, heart failure, obesity (body mass index above 30), autoimmune or systemic disease, urological disease, a family history of progressive kidney disease, a past acute kidney injury, past kidney-toxic treatment (including NSAIDs), iodinated contrast or radiotherapy near the kidneys, and occupational exposure to lead, cadmium or mercury.

Creatinine and eGFR

Creatinine is a waste product of muscle activity. A blood creatinine result is turned into an estimate of how well the kidneys filter, using an equation that, as the CDC explains, also takes age and sex into account. It is an estimate. KDIGO lists situations where it is less accurate, such as very low or very high muscle mass, eating disorders or some diets; and a single low value may reflect a recent acute injury rather than a chronic disease.

An eGFR is compared with previous results and read alongside the other markers. The general method, including checking units and past values, is in our guide on how to read blood test results.

Urine albumin and the ACR

Albumin is a protein that is normally barely present in urine; its presence can signal kidney damage. Dividing the urine albumin by the urine creatinine means a single sample is enough, without a 24-hour collection. KDIGO prefers a first-morning midstream sample, and asks for an elevated ACR on a random sample to be confirmed on a first-morning one.

A rise can be temporary. MedlinePlus, the consumer health site of the US National Library of Medicine, notes that exercise, certain medicines, fever and inflammation, including a urinary tract infection, can increase urine albumin for a short time. Mention them when you give the sample: a single urine test cannot establish a chronic disease.

KDIGO asks for tests to be repeated to confirm CKD after an unexpected finding, and defines chronicity as a duration of at least three months. It warns against assuming chronicity from a single abnormal eGFR or ACR, which could reflect an acute kidney injury. Proof can come from past results, imaging, medical history or repeat measurements within and beyond the three-month point.

France puts a timeframe on it: the HAS confirms the diagnosis by repeating the tests within the three months that follow an abnormal finding, and the Assurance Maladie suggests using the same laboratory where possible. If the abnormality is confirmed, further tests follow, such as a urine culture and a kidney ultrasound, and the cause is investigated.

Referral to a kidney specialist depends on several criteria; the HAS lists the cause, the stage, a rapid decline in GFR, severe or persistent albuminuria and uncontrolled blood pressure. A slightly abnormal result does not automatically mean a specialist appointment, but a severe or fast-moving decline should never be brushed aside.

KDIGO calls for a comprehensive strategy to reduce the risk of progression and its complications. It encourages physical activity suited to each person’s heart health, tolerance and frailty, an optimal weight and not using tobacco.

Advice on salt, potassium, phosphorus or protein is not universal: KDIGO wants it tailored to the person, the severity of the disease and other conditions, ideally with a renal dietitian. The same goes for fluids: the NHS notes that some people with CKD are advised to cut back on salt and fluids to ease swelling. KDIGO also recommends reviewing over-the-counter medicines and herbal or dietary remedies that may be harmful to people with CKD, so mention them.

A complete list of medicines

Medication safety is part of prevention. KDIGO asks clinicians to take GFR into account when dosing medicines cleared by the kidneys, and the NHS advises people with kidney disease to avoid over-the-counter NSAIDs unless a professional says otherwise. Never stop a prescribed treatment on your own: keep an up-to-date medication list, including self-medication and supplements, and ask your pharmacist or doctor.

Results become useful over time. Keeping successive results shows whether eGFR is stable, slowly declining or dropping. For people with CKD, KDIGO considers that a change in eGFR of more than 20% from one test to the next, or a doubling of the ACR, exceeds the expected variability and warrants evaluation.

The same principle applies to blood pressure, which your doctor may ask you to track yourself: our guide to home blood pressure monitoring explains how to get reliable readings.

In MyTwin for patients, your lab results are gathered with your other health documents, in chronological order and linked to their original report, so your successive eGFR and ACR results are easy to find. Interpreting them remains the job of the doctor who follows you.

Bring your previous test results, your list of medicines, any blood pressure readings you were asked to take, and recent events: infection, fever, hard exercise before the test, a hospital stay, a scan with contrast dye. Note any family history of kidney disease and relevant workplace exposures. For the rest, see our guide on how to prepare for a doctor’s appointment.

Questions worth asking:

• Am I in an at-risk group?
• Have both screening tests been done?
• Should the result be repeated, and when?
• How does it compare with my previous results?
• Do any of my medicines need adjusting?
• Which signs should make me seek care sooner?