Chronic kidney disease

Recently the College distributed a new set of guidelines: ‘Promoting good CKD management’.1 Raising awareness of chronic kidney disease (CKD) is a good thing as CKD often goes unrecognised in primary care.2 People with CKD are at higher risk of cardiovascular disease and all cause mortality is also increased.3^–5 Strict control of blood pressure improves outcome,6 angiotensin-converting enzyme inhibitors (ACE-I) and angiotensin receptor blockers (ARB) are particularly effective.7

There are two points in the guidance which need careful consideration. Firstly it may be unhelpful to a glomerular filtration rate (GFR) of 100ml/min/1.73m² as normal. Secondly, it may not be cost-effective to require the 6% of the population, who with the advent of reporting estimated GFR have been newly been diagnosed as having CKD (eGFR<60ml/min/1.73m²), to all have a parathyroid hormone (PTH) tests.

While the mean GFR in adult kidney donors up to age 40 years has been reported normally distributed with a mean of 100ml/min/1.73m² (SD = 15)8 the population in general practice who have their creatinine measured, and therefore GFR estimated, may be unwell or being tested as part of a chronic disease management programme.

In a registered GP population of approximately 50 000 people 26% (28% women and 22% men) had their GFR estimated. The mean eGFR for was men 75.6ml/min/1.73m² (SD = 19.0) and for women 69.2 ml/min/1.73m² (SD = 20.2). Only males aged 20–24 years have a mean eGFR at the ‘normal’ level quoted; and a majority of women over 75 years and men over 80 years have eGFR <60ml/min/1.73m². However, loss of renal function with age is largely attributable to hypertension; CKD should be treated with aggressive risk factor reduction regardless of age.9

Only 13 women and three men in the sample have a record of having their PTH tested. PTH tests cost between £12 and £18; and it is recommended that if PTH is raised a vitamin D blood test, costing a further £10 to £19, is carried out. Before everyone with newly diagnosed CKD (eGFR <60 ml/min/1.73m²) is sent for a PTH tests, careful appraisal is needed of the evidence-base for these tests. The potential benefit of early detection and treatment is that hyperparathyroidism is associated with low vitamin D levels,10 which, in turn, predisposes to poor bone mineral density and fractures.11 These changes may be amenable to reversal by the administration of calcium and vitamin D. However, there is limited evidence that early detection of renal osteodystrophy in people with stable moderate CKD improves outcome.12

In summary, GPs should expect that around 6% of their practice population (8.5% of women and 4% of men) to have CKD. While disturbance of bone and mineral metabolism offers an avenue for intervention in terms of improving biochemical markers, further research is needed to know whether outcomes are improved in this group. A pragmatic approach would be to measure PTH in all new diagnoses of stage 4 and 5 CKD (eGFR <30ml/min/1.73m²) and in stage 3 (30–59ml/min/1.73m²) where deteriorating renal function leads to referral. Meanwhile management of cardiovascular risk in CKD should remain paramount. GPs should concentrate on tight control of blood pressure, ideally using ACE-I or ARB and conduct medication reviews as suggested in this guidance.

• © British Journal of General Practice, 2006.