Can osteoporosis be diagnosed in patients with CKD?
Osteoporosis is a condition of decreased bone mass, leading to fragile bones, which are at an increased risk for fractures. The diagnosis of osteoporosis is generally based on measurements of bone mineral density (BMD).
The World Health Organization (WHO) has established criteria for making the diagnosis of osteoporosis. These criteria are based on comparing the BMD of the patient with that of a typical healthy, young gender-matched adult. BMD values that fall well below the average for healthy young adults (stated statistically as 2.5 standard deviations below the average referred to as the T-score) are diagnosed as osteoporotic.
Although these criteria are widely used, they were based and validated only on Caucasian females. Furthermore, underlying diseases, such as chronic kidney disease, were excluded from the analyses.
In non-CKD populations, fracture risk increases approximately 1.6-fold for every SD decrement in BMD, irrespective of gender. Although CKD patients have decreased BMD, the degree of bone loss is not directly associated with the decrease in estimated GFR.
Furthermore, BMD measurements are not able to discriminate between the histological or microarchitectural abnormalities seen in CKD and thus have not been able to consistently discriminate between CKD patients who fracture and those who do not fracture.
It is important to remember that there are many potential causes for decreased bone density in CKD patients, including hypogonadism, sedentary lifestyle, smoking, use of steroids, poor protein intake, vitamin D deficiency, diabetes, and Ca deficiency.
Thus in CKD patients, fractures are not necessarily related to osteoporosis, and the diagnosis could only be made after ruling out and correcting all underlying causes of CKD-MBD and generally requires a bone biopsy prior to proceeding with traditional anti-osteoporotic therapy.