Calcium to creatinine clearance ratio

Investigation Protocol

Indication

To screen for familial hypocalciuric hypercalcaemia and quantify urinary calcium excretion.

Preparation

The patient may eat and drink normally prior to the test. Written instructions must be given to the patient prior to performing this test to ensure the 24 hour collection is performed accurately.

Procedure

The patient is informed to start a urinary collection, into a plain bottle, 24 hours prior to attending.

Patients are advised to empty their bladder into the toilet normally on waking that morning. From that time onwards, all urine passed that day should be collected into a collection bottle. All urine passed during that night should also be collected. The following morning, when the patient wakes, they should empty their bladder and collect this as the final sample into the same bottle, so that they start and finish the collection with an empty bladder.

On the second day, the patient should bring their completed urine collection with them, and have a single blood test taken into a plain clot tube, for calcium, urea, creatinine and electrolytes (and magnesium when requested).

The blood and urine samples should be labelled and sent together for analysis and calculation of calcium to creatinine clearance ratio.

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Patient information sheet

Calcium to creatinine clearance ratio

Your doctor has asked us to coordinate a blood and urine test to measure the way your kidneys handle calcium. This is to determine whether your parathyroid or calcium glands are overactive, and whether this is affecting your kidneys.

It is very important that the test is completed accurately, so that every time you pass urine, it is all collected as this will affect the results of your test. It is also important that you have the blood test taken on the same day as your urine collection.

First identify a day which is suitable: it is probably easiest if there is a day you are not planning to go out on to perform this test. You can then bring the urine sample with you the following morning to have the blood test taken at the same time.

Please take all your medication as normal, and you may also eat and drink as normal on the day of this test. The easiest way to start is to empty your bladder into the toilet normally when you wake up on the morning that you start a collection, and note the time. From that time onwards, all urine passed that day should be collected into a plain collection bottle. All urine passed during that night should also be collected.

We recommend that you set an alarm if necessary to wake you up by the same time the following morning. The following morning, you should empty your bladder, but collect this as the final sample into the same bottle as from the previous day. This means that you start and finish the collection with an empty bladder at the same time each day. Please bring the sample and forms with you to have the final blood test performed that morning. 

If you have any queries about the test, please contact: 

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