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CKD guidance: A quick guide to recent changes

GP Dr Kathryn Griffiths presents a quick guide to making sense of the new NICE guidance on chronic kidney disease

GP Dr Kathryn Griffiths presents a quick guide to making sense of the new NICE guidance on chronic kidney disease

41208912It's been a busy year of changes to the primary care management of chronic kidney disease (CKD). The Department of Health's 18-week Commissioning Pathway for Chronic Kidney Disease 2008 was published in May and laid out new referral criteria. And late last month, NICE published its long-awaited guidance. This article lays out how the major changes in both documents will affect GP management of the disease – particularly CKD stage 3.

Changes to the definition of CKD stages 3 to 5

eGFR is now reported routinely along with the creatinine result, and laboratory assays are calibrated to an agreed standard. If the eGFR is greater than 60ml/min/1.73m2 this should be interpreted ‘with caution', according to NICE, which recommends that laboratories should not report actual values at this level. If the value is less than 60ml/min/1.732 for the first time, the test should be repeated within two weeks. A patient should not be labelled as having CKD without at least two values at least 90 days apart.

Factors affecting eGFR testing

There are several new and important factors to note about eGFR testing.

Samples should be taken from well hydrated patients who have not consumed a lot of cooked meat – such as a full English breakfast – before the test.

It is important to correct the value for ethnicity by multiplying the result by 1.21 for people of African or African-Caribbean ethnicity. There is currently no recommendation for other ethnic groups although there are studies under way.

Where there are extremes of muscle mass, for example with body-builders, anorectic patients or amputees, the result will not reflect true kidney function.

Subdividing stage 3

CKD stage 3 is now subdivided to focus on those at highest risk.

Most CKD patients in primary care will have an eGFR between 45-60ml/min/1.73m2, now classified as CKD 3A. They are likely to be elderly and there is debate about the significance of their CKD. Studies show that the method of calculating eGFR – the MDRD equation – is as accurate in the elderly and that they are as likely to progress to end-stage kidney disease as younger people.

But evidence shows that people with eGFRs of 30-44 (CKD 3B) are much more likely to have progression of their kidney disease and cardiovascular and metabolic complications.

NICE guidelines recommend that we focus on patients who would need renal replacement therapy if their decline in GFR continued at the observed rate (see table below).

41208913Frequency of eGFR testing

People with CKD 3 should have eGFRs checked every six months. Those with CKD 4 should be checked every three months and CKD 5 every six weeks.

People considered at risk of developing CKD should have an annual blood test with measurement of serum creatinine levels. People considered at increased risk are those with:

• hypertension

• diabetes

• cardiovascular disease, especially with heart failure

• structural renal tract disease, renal calculi or prostatic hypertrophy

• multisystem disease with potential kidney involvement, for example SLE

• a family history of CKD stage 5 or hereditary kidney disease

• haematuria or proteinuria.

Also at risk are those who are:

• taking nephrotoxic drugs such as lithium

• receiving long-term NSAID medication.

Changes to testing for proteinuria

All patients with CKD, or at risk of CKD, should be assessed annually and monitored using albumin-to-creatinine ratio (ACR).

This is recommended because it is more accurate and specific than protein to creatinine ratio (PCR), although more expensive. PCR can be used where there are high levels of proteinuria for monitoring. The values are not the same.

ACR is best measured using an early morning urine sample and if the level is greater than or equal to 30mg/mmol and less than 70mg/mmol it should be repeated to confirm the finding.

An ACR of greater than or equal to 30mg/mmol is considered clinically significant. In people with diabetes, microalbuminuria with an ACR higher than 2.5mg/mmol in men and 3.5mg/mmol in women is considered significant.

Using proteinuria to guide A-drug prescribing

The presence of microalbuminuria in people with diabetes is an indication for the use of an A-drug, an ACE inhibitor being the first choice with ARBs reserved for patients intolerant of ACE inhibitors.

When the ACR is 30mg/mmol or greater and the patient has hypertension, an A-drug is recommended as first line. The recommended BP target is below 140/90mmHg.

If ACR is 70mg/mmol or greater in a person with CKD, an A-drug is recommended to reduce the progression of kidney disease, even if blood pressure is considered normal and there is no other evidence of CVD. In these people, and also those with diabetes and CKD, a blood pressure target of less than 130/80mmHg is recommended.

Use of these drugs is likely to be associated with a rise in creatinine levels one to two weeks after initiation of an

A-drug or any change in dose. A fall of less than 25% in eGFR or an increase in creatinine of less than 30% does not require a change in the dose but should be repeated after a further one to two weeks. If the change is above this level another cause should be considered such as dehydration or NSAID use. Renal artery stenosis should be considered, particularly when the patient has other evidence of atherosclerosis. If no cause can be found, the drug should be stopped or reduced to previously tolerated levels. Trial evidence suggests that high doses of these drugs are required to give the maximum benefit in reduction of proteinuria and progression of CKD.

CKD, hypertension and QOF

The clinical indicators for the QOF were changed in April 2008.

The audit standard is unchanged at 140mmHg systolic and 85mmHg diastolic – the lowest for any chronic condition. There are no lower standards for people with proteinuria or a reward for measuring proteinuria. CKD 4 has been lost and moved into CKD 5. This makes it clearer that the A-drug indicator only includes patients with CKD, hypertension and proteinuria.

Cardiovascular risk and CKD

A study in 2004 showed that a patient with CKD 3 will have a five-year risk of requiring renal replacement therapy of 1.1% but a 24.3% risk of death – largely through cardiovascular disease1.

Conventional risk tables underestimate the additional risk associated with CKD, although the presence of proteinuria indicates end organ damage and a five-year CVD risk of greater than 20%. QRISK 2 does include a factor for CKD but we are waiting for more validation studies before this is introduced into practice.

Lifestyle advice must remain the cornerstone of risk reduction with the patient being encouraged to take exercise, achieve a healthy weight and stop smoking. Smoking is a risk factor both for CVD events and the progression of CKD.

Statins are recommended for the secondary prevention of CVD whatever the baseline cholesterol levels, although more evidence for their use in primary prevention in CKD is awaited.

Low-dose aspirin is safe and effective in people with CKD, but there is increased risk of bleeding where multiple antiplatelet drugs are used.

Metabolic complications of CKD

Serum calcium, phosphate or parathyroid hormones do not need to be checked in people with CKD stages 1-3.

Anaemia is uncommon in people with CKD stage 3 without diabetes. The advice from NICE is to check haemoglobin in those with CKD stages 3B, 4 and 5 to identify anaemia (haemoglobin less than 11.0g/dl).

It is important to remember that these patients can also develop iron-deficiency anaemia. Iron status should be checked before assuming that they have renal anaemia and iron deficiency investigated appropriately.

Indications for referral

People with CKD stages 4 and 5 should normally be considered for referral for specialist assessment. Proteinuria with an ACR higher than 70 mg/mmol is an indication for referral, as is proteinuria higher than 30 with co-existing haematuria.

Progression of CKD is defined as a fall in eGFR of more than 5ml/min in one year or more than 10ml/min in five years – and these patients should be considered for referral.

Patients thought to have a rare or genetic cause or renal artery stenosis should also be referred.

Failure to achieve satisfactory BP control despite the use of four agents in maximally tolerated doses is another indication.

Some nephrology services offer internet-based support to primary care and this is a suitable alternative to referral. It is important that people who have a more severe decline in eGFR are referred early because they may be suitable for a pre-emptive renal transplant, a procedure that will improve both their quality and quantity of life.

Other patients may believe that nephrology specialist services have nothing to offer because they would never accept renal dialysis. I have had several very elderly patients with an eGFR of less than 10 who have benefited enormously from the conservative care approach offered by the team here in York. They have had their anaemia treated with erythropoietin and more importantly they and their families have been supported by the palliative care advice offered by the team.

Dr Kathryn Griffith is a GP in York and primary care lead for the CKD pathway

Patients with CKD 3 should have eGFRs checked every six months Patients with CKD 3 should have eGFRs checked every six months Key messages Staging

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