The criteria for determining CKD is very confusing to me. As you know, the Merck Manual lists 5 stages of CKD. From reading some of your past posts it appears that you consider eGFR 60 or above to be normal. I have read that one of the following must be present for > or = three months to be CKD: GFR 29, or other markers of kidney damage. According to this criteria, it appears to me that stages 1 & 2 of CKD as defined in the Merck Manuel are completely ignored. Please explain.The other question I have is that the National Kidney Foundation website states that 37, 000, 000 adults have CKD in the US. There is no explanation as to what that number includes. That seems to be a lot of people to be in stages 3,4, & 5 so does that number include stages 1 & 2?

There are 5 Stages of chronic kidney disease (CKD) that have been proposed by the National Kidney Foundation (NKF). The estimating equation that we use to calculate the estimated glomerular filtration rate (eGFR) is most accurate and consistent when the eGFR is 60 milliliters per minute per 1.73 meters squared or less. Hence, if we are going to use the eGFR only to make a diagnosis of CKD, it is best when the eGFR is less than or equal to 60.

Stage 1 CKD is indicated when there is abnormal urine (such as blood, protein or infection) that is present for at least three months, there is an abnormal ultrasound such as polycystic kidney disease or an abnormal kidney biopsy AND the eGFR is normal at between 90 and 120. Stage 2 CKD is indicated by urine or ultrasound abnormalities or a kidney biopsy that is abnormal for at least three months AND the eGFR is between 60 and 89. Stage 3 CKD is diagnosed if the eGFR is between 30 and 59 AND is present for at least three months. No urinary or other findings are required but are confirmatory for CKD. Stage 4 CKD is an eGFR between 15 and 29 for at least three months. Stage 5 CKD is an eGFGR less than 15 and present for at least three months.  You can learn more about CKD Staging at our web site at:

The estimate for CKD recently posted on the NKF web site is from the Centers for Disease Control and can be found at:

A majority of the people with CKD are in Stage 1 or 2 and unaware of their kidney disease.

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