The assessment of renal Ca excretion is commonly used for the differential diagnosis of causes of hypo- and hypercalcemia.[i] While determining the amount of Ca excreted in 24-hour urine collections is the gold standard for evaluating Ca balance, the estimation of the urine-calcium-to-urine-creatinine (uCa/uCrea) concentration ratio in first-void urine in the morning correlates well with the 24-hour urine Ca excretion measurements.[ii]

Ca homeostasis is maintained mainly by the well known physiological mechanism that the kidneys excrete approximately the same amount of Ca that is absorbed by the intestine during a 24-hour period.[iii] However, in a variety of disorders renal Ca loss may be higher than Ca uptake by the body. This state of hypercalciuria may be caused by Vitamin D deficiency due to insufficient intake or malassimilation as a consequence of numerous gastrointestinal diseases.[iv] Also, a variety of metabolic disorders including diabetes mellitus may be associated with enhanced renal Ca loss. Furthermore, hormonal disorders including those of postmenopausal women as well as lack of physical activity and drug side effects often lead to hypercalciuria and sometimes severe osteoporosis.

Osteoporosis is a common bone disorder that may principally affect females and males of any age. In particular, more than 30% of all postmenopausal women suffer from clinically relevant osteoporosis with increased risk for bone fractures. Currently, the most widely accepted method for diagnosing osteoporosis is the determination of bone mineral density (BMD). However, BMD measurements are technologically and logistically demanding, time- consuming and expensive. Other markers of osteoporosis, such as ß-crosslaps and Ca excretion in 24-hour urine collections are used clinically to assess responses to treatment, however, these investigations are cumbersome and error-prone, with considerable overlap of results between matched normals and osteoporosis patients. Thus these methods are not well suited for general population screening of increased Ca loss associated with osteoporosis. The patients do not have the chance to monitor themselves!

Contrary to hypercalciuria, a decreased excretion of Ca, i.e. hypocalciuria, has been reported to be a mechanism in pre-eclampsia,[vi] which is one of the major causes of maternal death. Pre-eclampsia affects up to 8% of pregnancies worldwide. Already in earlier years, the urine-Ca-to-urine-creatinine (uCa/uCrea) ratio was demonstrated to be significantly lower in pre-eclamptic pregnant women.[vii]

Clinically useful Ca status screening and monitoring using the uCa/uCrea ratio in spot urine samples is therefore suggested to be very helpful in the following patient groups:

Ca-PoCT market potential focused
“only” on patients with high medical need