Chronic Kidney disease: Avoiding overdiagnosis
Written by Dr Jonathan Kwan for Doctify
Tell someone they’ve got “chronic kidney disease” (CKD) and they’re likely to fear the worst: dialysis machines and waiting for a kidney transplant. However, most people who are told they have CKD won’t need these treatments and some are even mislabelled as having this condition when in fact they have normal healthy kidneys. Erroneous diagnosis of CKD on an individual can lead to untold consequences, both clinical and socio-financial. These include unnecessary and avoidable investigations on top of the inconvenience of attending repeated clinic visits; occupation health declaration may compromise job application for some categories of jobs; unjust premiums on life and travelling insurance; failed mortgage applications and problems with fostering and adoption approval. These are some of the stories one hears from patients!
CKD is classified from stage one to five according to someone’s eGFR. This is an estimate of how well the kidneys are filtering waste from the blood into the urine. Being able to do this with a simple blood test (using serum creatinine to calculate the eGFR) was a milestone event in helping health professionals recognise CKD as a public health concern because of the association between CKD and heart disease, stroke and other medical problems. However, all the formulae used for eGFR estimation have significant limitations and suboptimal accuracy leading to misclassification and over-diagnosis, particularly in the failure to incorporate an age-based approach to the diagnosis and classifications.
Although an average decline in GFR after age 50 is thought to be at approximately 1 ml/min per year, many exceptions confound this generalisation. Strictly speaking, the MDRD eGFR does not apply in extremes of ages (under 18 or over 70), or people with unstable or rapidly changing creatinine concentrations as seen in acute kidney injury. Other exceptions include pregnancy, serious co-morbid conditions, extremes in muscle mass and diet, paraplegia, bodybuilding, and morbidly obesity.
Many medical practitioners often are not aware that in the absence of structural kidney abnormalities (e.g. polycystic or dysplastic kidneys) or urinary abnormalities (e.g. haematuria or proteinura) people with eGFR below Stage 3 (i.e. eGFR over 60 ml/min) cannot be classified as suffering from CKD. Someone with a small stature with perfectly normal kidney health are often found to have eGFR in the range of around 60 ml/min.
In summary, caution and common sense should be exercised to avoid inflicting unwarranted anxiety and needless medical evaluations that accompany CKD misdiagnosis. CKD is an important medical condition that doctors should diagnose carefully and discuss sensitively with patients.