Thank you very much for your email and highlighting the errors in the guidelines.
24h urine collections are not often collected completely. I am based in a centre that undertakes a significant number of parathyroidectomies. In our Endocrine MDTs we work-up our patients carefully aiming to exclude familial hypocalciuric hypercalcaemia (FHH) as surgery is not indicated in these patients. We use spot urine samples admittedly due to the vagueness of the available evidence and partly out of convenience. Over the last few years, in borderline cases, that is a calcium creatinine clearance ratio (CCCR) of slightly below the suggested cut-off 0.01 (uncertainty of measurement notwithstanding) I started requesting 24h urine calcium collections to check for concordance. In our experience, we have never seen any difference. In some cases, where doubt persisted we sent samples to Prof. Thakker’s laboratory in Oxford for FHH genetic testing to check for variants in the calcium sensing receptor. We have accumulated some data that concludes there is no difference between spot and 24h urine samples for FHH. In fact, we found 24h urine samples problematic taking incomplete urine collection and dilution with acid in short collections into account.
Following these observations and given the paucity in the literature, one of my MSc students will be undertaking a project (which has REC ethics approval) of which this will be one area she will be looking at. We hope to share our data early next year.
Dr R Sodi
Consultant Clinical Biochemist & Honorary Lecturer
Sent from my iPad
> On 12 Jun 2019, at 10:48, Kathy Richmond <[log in to unmask]> wrote:
> 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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