Dear all,
When looking at urine calcium excretion some decades ago, we noted:
That urine calcium/creatine ratio was higher in the first urine passed in the morning and also in the second passed 30 minutes later (presumably urine collecting in the renal pelvices overnight) than in a subsequent fasting 2 hour urine collection collected over the subsequent 2 hours after a glass of water. We assumed this was due to release of calcium from resting bone when in a recumbent posture overnight. This was previously described by Professor Nordin as part of a protocol for the calculation of calcium and phosphate excretion indices to assist in the diagnosis of hyperparathyroidism in the days before we had PTH assays.
During the day urine calcium/creatinine ratio depends on the dietary intake of different calcium salts with calcium citrate (found in milk) being better absorbed than that from some other more insoluble salts such as calcium phosphate.
All these variables contribute to the 24 hour calcium excretion when eating an unrestricted diet.
Kind regards
David
Dr David Cowley (retired)
Brisbane.
Effect Of Citrate On The Urinary Excretion Of Calcium And Oxalate: Relevance To Calcium Oxalate Nephrolithiasis. Cowley DM, McWhinney BC, Brown JM, Chalmers AH. Clin Chem 1989; 35: 23 - 28.
Clin Chem. 1989 Jul;35(7):1541. Effect of oral citrate on calcium absorption after an oral load of calcium phosphate.
de Leacy EA1, Cowley DM, Brown JM, McWhinney BC, Chalmers AH.
-----Original Message-----
From: Clinical biochemistry discussion list <[log in to unmask]> On Behalf Of Kathy Richmond
Sent: Wednesday, 12 June 2019 7:49 PM
To: [log in to unmask]
Subject: Nice guidance hyperparathyroidism May 2019
Dear mailbase
Not sure how many have read this yet but I'd like to make raise some points for discussion...(I reviewed the literature on this last month for our own clinicians).
Typo in section 1.1.8
seek specialist advice.... if the PTH is "below the mid point of the reference range" with an adjusted calcium >=2.6 -should be "above"
More importantly the advice on spot urines.
The paper quite rightly refers to Chrisstensons paper in 2018 as the only paper that compares calcium excretion indices in genetically and surgically proven cohorts of FHH and hPTH. This paper used 24 hr urines and the indices included ca/cr ratio on a 24 hr urine.
The expert panel then state that you can use spot urines and the evidence summary describes the evidence level as 'they felt' that there would be no difference between spot & 24 hr urine ca/cr ratios. There is direct evidence against this statement published by Cegla in 2010: using a credible cohort of patients and a review of the literature published by A Jones in Osteoporosis International 2012 . As well as numerous papers that show correlations but which are not clinically usable to exclude hypercalciuria. There is ample scientific evidence that ca/cr ratio in spot urines varies with creatinine level, fasting status and time of day etc etc
I have looked at this quite hard as spot urine measurements would be more convenient.
Given the strength of the evidence against the use of spot urines the reliance on 'felt' is entirely disappointing I would advise caution regarding accepting this statement at face value
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