Blog entry by Meguid El Nahas
MAREMAR STUDY: CKD CLASSIFICATION, TIME TO RE-THINK?
The MAREMAR study of CKD diagnosis and detection in Morocco is now published. This long awaited publication is an example of good quality epidemiology aimed at defining the prevalence of true CKD in Morocco.
A stratified, randomized, representative sample of 10,524 participants was studied. Weight, height, blood pressure, proteinuria (dipstick), plasma creatinine, estimated glomerular filtration rate, and fasting glycemia were measured.
Also, testing was repeated within 2 weeks and eGFR reassessed at 3, 6 and 12 months.
More interestingly, the authors compared “CKD” as defined by the cut off definition of KDOQI/KDIGO of 60ml/min to a more age-sensitive and more sensible classification based on the deviation from the percentile range for age; less than 3rd percentile.
This study highlights major points:
- Upon re-testing (Dipstix testing and/or eGFR) at 3 months, as recommended by KDOQI CKD definition and classification, 25-30% were found to be false positive and no longer classified as suffering from CKD; a sobering lesson for all those “epidemiological” reports of CKD prevalence that test the population ONCE and claim to define prevalence rates of CKD…RE TESTING IS A MUST TO DEFINE CKD.
- More interestingly, when CKD was defined as eGFR levels below the 3rd percentile for the individual's age-sex matched population, the study highlighted the serious shortcomings of the current cut off of 60ml/min/1.73m2 that is currently applied to all ages and genders: The MAREMAR showed that for younger individuals the current classification based on the 60ml/min arbitrary cut-off point, significantly UNDERDIAGNOSED CKD, whilst in older individuals over the age of 60 years, the current cut off significantly OVERDIAGNOSED CKD, mainly in those previously classified as CKD3A.
- When a study such as MAREMAR, that is well conducted with expertly validated methodologies, is undertaken, the prevalence of CKD (eGFR <60) falls to as low as 1.6% of the general population, a value well below the misleading prevalences reported in other poorly conducted studies claiming ~5-10%. Also, proteinuria is detected consistently in as few as 1.3%, again a prevalence well below the values previously branded upon single testing for ~7-10%.
MAREMAR is a landmark publication and a must read for all those aspiring to do epidemiological surveys on CKD in their populations. It shows that well conducted epidemiological studies can be undertaken. It also shows how they should be conducted with careful validation of methodologies and interpretation of results.
MAREMAR shows that CKD classification based on a SINGLE 60ML/MIN CUT OFF POINT FOR ALL AGES IS NOT FIT FOR PURPOSE; age and gender sensitive classification based on deviations from age and gender specific population norms (percentiles between 3-97th) is the way forward. This can be easily automated and reported. It will free millions worldwide from the misleading label of “CKD” based on an artificial and arbitrary cut off point.
IT IS HIGH TIME WE, AS NEPHROLOGISTS, RE-THINK THE CKD DEFINITION.